A new apparatus was designed to measure the electromagnetic force and a computational study of the traveling magnetic field(TMF)and its application to the Ga-In-Sn melt(with low melting point),then the forces on Al,Mg...A new apparatus was designed to measure the electromagnetic force and a computational study of the traveling magnetic field(TMF)and its application to the Ga-In-Sn melt(with low melting point),then the forces on Al,Mg,and Li melt,were simulated. The result show that the electromagnetic force on the melt increases linearly with the increasing length of the melt in the TMF.The TMF-induced Lorentz force increases with increasing frequency,and then decreases.The maximum value is obtained when the current frequency is 160 Hz,over that frequency the force decreases rapidly.When the iron-core is activated,the force increases when the melt closes to the iron-core.The Lorentz forces have inversely-proportional relationships with the electrical resistivity,the dfx/dρdecreases and the dfy/dρincreases with the increasing electrical resistivity(df/dρis the slope of the Lorentz force profile).展开更多
Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force ap...Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force applied by the metal melt exerts on the pri mary phase when the movement of the melt in the direction of electromagnetic force is limited. As a result, the repulsive force exerts on the primary phase to push them to move in the direction opposite to that of the electromagnetic force when the metal melt with primary phase solidifies under an electromagnetic force field. Based on this, a new method for production of in situ surface composite and gradient material by electromagnetic force is proposed. An in situ primary Si reinforced surface composite of Al-15wt%Si alloy and gradient material of Al-l9wt%Si alloy were produced by this method. The microhardness of the primary Si is HV1320. The reinforced phase size is in the range from 40μm to 100μm. The wear resistance of Al-Si alloy gradient material can be more greatly increased than that of their matrix material.展开更多
This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based o...This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.展开更多
All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravit...All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravity. In order to "push" the molten metal into the weld, a new kind of U-frame excitation model, which could produce electromagnetic force to balance the gravity of the molten pool, was designed. The related parameters of the excitation model were simulated by Maxwell 3D, and the relationships between the parameters and the magnetic induction intensity were analyzed. Finally, the electromagnetic force in the molten pool was calculated, and the appropriate parameters of the U-frame excitation model were determined. The results of the simulation verify the feasibility of the all-position welding excitation model.展开更多
Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces.Finite 3-D model of the coil-deposition layer-substrate was established.Simulation results show that the electromagnetic forc...Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces.Finite 3-D model of the coil-deposition layer-substrate was established.Simulation results show that the electromagnetic force in deposition layer mainly concentrates in the projection area of the coil.Axial electromagnetic force shows repulsion in one cycle.The experimental results indicate that the magnetic field is beneficial for grain refinement,microhardness increasement and decline of quantities and average sizes of pores.展开更多
According to the principle of electromagnetism and hydrodynamics,a mathematical model of flow field for metallic fluid acted by electromagnetic and centrifugal forces was established.The calculation results showed tha...According to the principle of electromagnetism and hydrodynamics,a mathematical model of flow field for metallic fluid acted by electromagnetic and centrifugal forces was established.The calculation results showed that the relative velocity between metallic fluid layers rises and the absolute rotational velocity of metallic fluid falls with the increase of magnetic induction intensity.The increase of centrifugal revolution hardly affects the relative velocity between metallic fluid layers,but can enhance the absolute rotational velocity of metallic fluid.展开更多
In modern processing of conducting materials, such as steel,the time-varying electromagnetic field plays a key role in obtaining the desired microstructure or eliminating solidification defects such as porosity and se...In modern processing of conducting materials, such as steel,the time-varying electromagnetic field plays a key role in obtaining the desired microstructure or eliminating solidification defects such as porosity and segregation in cast billets. Up to now,few studies on the induced electromagnetic force (also called the Lorentz force) field in liquid metal have been reported. Compared with the magnetic field, the induced force field is the real and only direct cause for flow control. The electromagnetic force is comprised of two components. One is time-independent and the other is time- dependent. The time-dependent component varies with time in both amplitude and direction. When it reaches the extreme value,it can be one dozen times larger than the time-independent component. In this paper, a new method to quantitatively describe the induced electromagnetic force in liquid metal under a harmonic electromagnetic field,including both its time- independent and dependent components, was proposed based on the formula derivation from the data of amplitude and phase angle. Through this method ,the features of the time-dependent component were discussed, including the directions of rotation and the long axis. As a result, the force pattern was described. With two example calculations, the method was explained in detail. The results of both examples show that the force field in liquid metal can be divided into several regions with different force features. Example 1 shows the effect of coil position on the evolution of the force field pattern in liquid metal. Example 2 is a kind of stirring by the travelling magnetic field ,whose results present the sub-structures in metal and show that most of them have almost the same rotating direction.展开更多
The particle migrating behavior at solidifying front is discussed in theory with the application of electromagnetic force field(EMFF), on the basis of foregone analysis of force upon particle ahead of solidifying fron...The particle migrating behavior at solidifying front is discussed in theory with the application of electromagnetic force field(EMFF), on the basis of foregone analysis of force upon particle ahead of solidifying front without electromagnetic force field. The critical solidification velocities of particle pushing/engulfment transition ahead of horizontal and vertical interface are derived respectively when a certain EMFF is applied. And the critical electromagnetic forces of particle pushing/engulfment transition ahead of horizontal and vertical interface are also derived separately when a certain solidifying velocity is given.展开更多
A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane(PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave...A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane(PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave lens form a coaxial compound lens system. The plane-concave lens equipped with driving coils is installed directly above the PDMS lens surrounded by the annular magnet. When different currents are applied, the annular magnet moves up and down, driving the PDMS film to undergo elastic deformation, and then resulting in longitudinal movement of the PDMS lens. The position change of the PDMS lens changes the focal length of the compound lens system. To verify the feasibility and practicability of this design, a prototype of our compound lens system is fabricated in experiment. Our proposed compound lens shows that its zoom ability reaches 9.28 mm when the current ranges from -0.20 A to 0.21 A.展开更多
The mathematical model of the solenoid valve under varying temperatures is constructed to investigate its performance and enhance heat dissipation balance.The relationship between temperature and electromagnetic force...The mathematical model of the solenoid valve under varying temperatures is constructed to investigate its performance and enhance heat dissipation balance.The relationship between temperature and electromagnetic force is determined.Electrothermal coupling simulation using COMSOL is conducted,optimizing the outer diameter and length structure parameters of the coil.It is established that the heat dissipation of the coil is influenced by its outer diameter.Subsequently,based on optimized coil structure parameters,an orthogonal experimental design method combined with Ansys Maxwell is employed for simulation solution analysis to study the impact of structural parameters such as length,position,front and rear angles of the magnetic barrier ring in the iron core,armature length,and through-hole size on electromagnetic force.Optimal structural parameters are identified.Results indicate a decrease in steady-state electromagnet temperature by 3-4℃,an increase in the initial electromagnetic force by 32.63%,and a rise in the maximum electromagnetic force by 27.10%.展开更多
To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process, ANSYS software was used to simulate electromagnetic force field and flu...To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process, ANSYS software was used to simulate electromagnetic force field and fluid velocity field in the alloy melt in a crucible tube in three coils. In the first section of the paper, eletromagnetic force field and fluid velocity field caused by single coil were simulated. The result of this simulation gives an average velocity of 3.2 cm/s and it is called critical velocity because a fluid velocity over it will cause a fine and spherical structure of solid primary a in a semi-solid melt. And, from this result, a reasonable temperature of semi-solid of the alloy and an electrical current intensity were established. The electrical current intensity of the result of this simulation corresponded to the current intensity used in a practice experiment, in which the primary α was obviously refined and sphericized. Based on this simulation of single coil electromagnetic stirring, in the second section of the paper, eletromagnetic force field and fluid velocity field caused by three coils were simulated. The result of the simulation shows that, 1) there is a semi-solid zone of 32 mm from bottom of the crucible tube to the upper; 2) the electrical current intensities of three coils of 400 A, 600 A, and 400 A, which were set to top range, middle range and bottom range of the tube, respectively, were the optimum parameters of electromagnetic current intensity under the condition of this investigation; and 3) under effect of these electromagnetic current intensity, the fluid velocities of the melt in the tube were 6.3 cm/s in top range, 3.75 cm/s in middle range, and 3.9 cm/s in bottom range of it, respectively.展开更多
The upper vertical stability (VS) feeder is a part connected to the upper VS coil by a welding joint. The function of the feeder is to transfer current and coolant water to the VS coil. A giant electron^agnetic forc...The upper vertical stability (VS) feeder is a part connected to the upper VS coil by a welding joint. The function of the feeder is to transfer current and coolant water to the VS coil. A giant electron^agnetic force will be generated during normal operation by the current flowing in the VS coils, interacting with the external background field. The Lorentz force will induce Tresca stress in the feeder. The amplitudes of the magnetic field and Lorentz force along the conductor running direction have been calculated based on Maxwell's equations. To extract the Tresca stress in the feeder, a finite element model was created using the software ANSYS and an electromagnetic load was applied on the model. According to the analytical design, the stresses were classified and evaluated based on ASME. In order to reduce the Tresca stress, some optimization works have been done and the Tresca stress has had a significant reduction in the optimized model. This analytical work figured out the stress distribution in the feeder and checked the feasibility of the prototype design model. The ANSYS analysis results will provide a guidance for later improvement and fabrication.展开更多
ELM (edge localized mode) coils are key components of ITER that suppress the edge localized mode phenomenon. A giant electromagnetic force is generated during normal operations by the current flowing in the ELM coil...ELM (edge localized mode) coils are key components of ITER that suppress the edge localized mode phenomenon. A giant electromagnetic force is generated during normal operations by the current flowing in the ELM coils interacting with the external background field. The Lorentz force will induce Tresca stress in the ELM coils. If the load goes beyond the allowable threshold, the coils can hardly satisfy the safety requirements. The right-hand bottom corner was chosen to perform our electromagnetic analyses. Based on the Maxwell equation, the detailed magnetic field and Lorentz force were calculated. By use of the finite element software ANSYS, the Tresca stress was extracted and evaluated based on our analytical design. The present analysis aims to verify the feasibility of the current design. It can also serve as guidance for fabrication and structural optimization.展开更多
Space electromagnetic docking technology, free of propellant and plume contamination, offers continuous, reversible and synchronous controllability, which is widely applied in the future routine on-orbit servicing mis...Space electromagnetic docking technology, free of propellant and plume contamination, offers continuous, reversible and synchronous controllability, which is widely applied in the future routine on-orbit servicing missions. Due to the inherent nonlinearities, couplings and uncertainties of an electromagnetic force model, the dynamics and control problems of them are difficult. A new modeling approach for relative motion dynamics with intersatellite force is proposed. To resolve these control problems better, a novel nonlinear control method for soft space electro-magnetic docking is proposed, which combines merits of artificial potential function method, Lyapunov theory and extended state observer. In addition, the angular momentum management problem of space electromagnetic docking and approaches of handling it by exploiting the Earth's magnetic torque are investigated. Finally, nonlinear simulation results demonstrate the feasibility of the dynamic model and the novel nonlinear control method.展开更多
In this paper,the effects of Lorentz force on drag reduction for a circular cylinder have been studied experimentally and numerically.Based on its effects on drag reduction,the Lorentz force is found to be classified ...In this paper,the effects of Lorentz force on drag reduction for a circular cylinder have been studied experimentally and numerically.Based on its effects on drag reduction,the Lorentz force is found to be classified into two parts:one acts directly on the cylinder,named as the wall Lorentz force,and the other called the field Lorentz force acts on the fluid inside the boundary layer.The wall Lorentz force leads to the generation of a thrust,whereas the field Lorentz force results in drag increase.Since the former dominates the drag variation,the drag would reduce accordingly and even turn into negative (thrust) with the application of Lorentz force.展开更多
The operating speed of the commercial electromagnetic suspension(EMS)maglev train has been over 430 km/h,making it the fastest means of land transportation.With the increasing demands of people traveling,it is necessa...The operating speed of the commercial electromagnetic suspension(EMS)maglev train has been over 430 km/h,making it the fastest means of land transportation.With the increasing demands of people traveling,it is necessary to further improve the operating speed of maglev trains.Aiming to examine whether the existing EMS system can meet the requirements of ultra-highspeed operation(more than 600 km/h),the electromagnetic characteristics of an EMS linear motor under the operating speed of 600–1000 km/h fed by a square-wave voltage supply is investigated in this article.First,an electromagnetic field model of the EMS system under the square-wave voltage supply is established to investigate its electromagnetic performance,e.g.,the characteristics of phase current,the magnetic flux density,and the electromagnetic force.Second,the relationship between the harmonic components of the air-gap magnetic flux density and electromagnetic force is investigated using the two-dimensional fast Fourier transform(2D-FFT)to reveal the mechanism of electromagnetic force ripple.Third,to address the issues of excessive armature current density and significant electromagnetic force ripple,the linear motor is re-designed by enlarging the stator slot area and reshaping the mover's main magnetic poles.Furthermore,the Taguchi method is used to further improve the electromagnetic characteristics of the linear electric motor.Finally,the effectiveness of the proposed optimal design is validated by the finite-element analysis(FEA)based co-simulation.展开更多
Some of the previous theories in the electrostrictive and magnetostrictive materials and their differences are discussed in this paper. A variational principle in the general thermodynamic sense is given and the gover...Some of the previous theories in the electrostrictive and magnetostrictive materials and their differences are discussed in this paper. A variational principle in the general thermodynamic sense is given and the governing equations can be derived from this principle. Illustrational examples are given.展开更多
A three-dimensional (3-D) transient model has been developed to investigate plasma deformation driven by a magnetic field and its influence on arc stability in a circuit breaker. The 3-D distribution of electric cur...A three-dimensional (3-D) transient model has been developed to investigate plasma deformation driven by a magnetic field and its influence on arc stability in a circuit breaker. The 3-D distribution of electric current density is obtained from a current continuity equation along with the generalized Ohm's law; while the magnetic field induced by the current flowing through the arc column is calculated by the magnetic vector potential equation. When gas interacts with an arc column, fundamental factors, such as Ampere's law, Ohm's law, the turbulence model, transport equations of mass, momentum and energy of plasma flow, have to be coupled for aria- lyzing the phenomenon. The coupled interactions between arc and plasma flow are described in the fl'amework of time-dependent magnetohydrodynamic (MHD) equations in conjunction with a K-~ turbulence model. Simulations have been focused on sausage and kink instabilities in plasma (these phenomena are related tO pinch effects and electromagnetic fields). The 3-D sjm- ulation reveals the relation between plasma deformation and instability phenomena, which affect arc stability during circuit breaker operation. Plasma deformation is the consequence of coupled interactions between the electromagnetic force and plasma flow described in simulations.展开更多
Most image segmentation methods based on clustering algorithms use singleobjective function to implement image segmentation.To avoid the defect,this paper proposes a new image segmentation method based on a multi-obje...Most image segmentation methods based on clustering algorithms use singleobjective function to implement image segmentation.To avoid the defect,this paper proposes a new image segmentation method based on a multi-objective particle swarm optimization(PSO)clustering algorithm.This unsupervised algorithm not only offers a new similarity computing approach based on electromagnetic forces,but also obtains the proper number of clusters which is determined by scale-space theory.It is experimentally demonstrated that the applicability and effectiveness of the proposed multi-objective PSO clustering algorithm.展开更多
A coupled model including electromagnetic field, fluid dynamic, heat transfer and solidification, is developed and applied to the numerical simulation of steel flow and solidification in a 100mm × 100mm soft-cont...A coupled model including electromagnetic field, fluid dynamic, heat transfer and solidification, is developed and applied to the numerical simulation of steel flow and solidification in a 100mm × 100mm soft-contact mold. In this study, the 3D finite difference method and non-staggered grid system for fluid flow with body fitted coordinate were employed. Numerical results show that the electromagnetic force mainly affects the steel flow at upper part of mold, especially in the vicinity of meniscus. There exist upward flows covering the surfaces of the billet due to the concentration of electromagnetic force on the upper part of the billet. This flows join together and form a downward flow near the SEN, so a distinct circulating flow zone is formed at upper part of mold. After applying electromagnetic force, the steel velocity is improved and the temperature is raised. The strong stirring of electromagnetic force on liquid steel makes the kinetic energy on free surface increase. It is clearly seen that the solidification start point shifts downward in soft contact mold. As a result, the initial shell thickness gets thin and the initial solidification shell length is shortened.展开更多
基金Project supported by the Program of Excellent Team in Harbin Institute of Technology,China
文摘A new apparatus was designed to measure the electromagnetic force and a computational study of the traveling magnetic field(TMF)and its application to the Ga-In-Sn melt(with low melting point),then the forces on Al,Mg,and Li melt,were simulated. The result show that the electromagnetic force on the melt increases linearly with the increasing length of the melt in the TMF.The TMF-induced Lorentz force increases with increasing frequency,and then decreases.The maximum value is obtained when the current frequency is 160 Hz,over that frequency the force decreases rapidly.When the iron-core is activated,the force increases when the melt closes to the iron-core.The Lorentz forces have inversely-proportional relationships with the electrical resistivity,the dfx/dρdecreases and the dfy/dρincreases with the increasing electrical resistivity(df/dρis the slope of the Lorentz force profile).
基金supported by the National Natural Science Foundation of China(Grant No.50001008)the China Postdoctoral Science Foundation.
文摘Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force applied by the metal melt exerts on the pri mary phase when the movement of the melt in the direction of electromagnetic force is limited. As a result, the repulsive force exerts on the primary phase to push them to move in the direction opposite to that of the electromagnetic force when the metal melt with primary phase solidifies under an electromagnetic force field. Based on this, a new method for production of in situ surface composite and gradient material by electromagnetic force is proposed. An in situ primary Si reinforced surface composite of Al-15wt%Si alloy and gradient material of Al-l9wt%Si alloy were produced by this method. The microhardness of the primary Si is HV1320. The reinforced phase size is in the range from 40μm to 100μm. The wear resistance of Al-Si alloy gradient material can be more greatly increased than that of their matrix material.
基金supported in part by the National Natural Science Foundation of China under projects 51907053by Natural Science Foundation of Jiangsu Province of China under Project BK20190489+1 种基金by the Fundamental Research Funds for the Central Universities under grant B200202167by the China Postdoctoral Science Foundation under grant no.2019M661708。
文摘This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.
基金This work was supported by the National Natural Science Foundation of China (No. 51075299).
文摘All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravity. In order to "push" the molten metal into the weld, a new kind of U-frame excitation model, which could produce electromagnetic force to balance the gravity of the molten pool, was designed. The related parameters of the excitation model were simulated by Maxwell 3D, and the relationships between the parameters and the magnetic induction intensity were analyzed. Finally, the electromagnetic force in the molten pool was calculated, and the appropriate parameters of the U-frame excitation model were determined. The results of the simulation verify the feasibility of the all-position welding excitation model.
基金supported by the National Science Foundation of China(No.51475238)the Jiangsu Science and Technology Support Program(No.BE2014009-1)the Jiangsu Provincial Key Research and Development Plan (Nos.BE201561,BE201603-3)
文摘Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces.Finite 3-D model of the coil-deposition layer-substrate was established.Simulation results show that the electromagnetic force in deposition layer mainly concentrates in the projection area of the coil.Axial electromagnetic force shows repulsion in one cycle.The experimental results indicate that the magnetic field is beneficial for grain refinement,microhardness increasement and decline of quantities and average sizes of pores.
基金Item Sponsored by National Natural Science Foundation of China(59995440)
文摘According to the principle of electromagnetism and hydrodynamics,a mathematical model of flow field for metallic fluid acted by electromagnetic and centrifugal forces was established.The calculation results showed that the relative velocity between metallic fluid layers rises and the absolute rotational velocity of metallic fluid falls with the increase of magnetic induction intensity.The increase of centrifugal revolution hardly affects the relative velocity between metallic fluid layers,but can enhance the absolute rotational velocity of metallic fluid.
文摘In modern processing of conducting materials, such as steel,the time-varying electromagnetic field plays a key role in obtaining the desired microstructure or eliminating solidification defects such as porosity and segregation in cast billets. Up to now,few studies on the induced electromagnetic force (also called the Lorentz force) field in liquid metal have been reported. Compared with the magnetic field, the induced force field is the real and only direct cause for flow control. The electromagnetic force is comprised of two components. One is time-independent and the other is time- dependent. The time-dependent component varies with time in both amplitude and direction. When it reaches the extreme value,it can be one dozen times larger than the time-independent component. In this paper, a new method to quantitatively describe the induced electromagnetic force in liquid metal under a harmonic electromagnetic field,including both its time- independent and dependent components, was proposed based on the formula derivation from the data of amplitude and phase angle. Through this method ,the features of the time-dependent component were discussed, including the directions of rotation and the long axis. As a result, the force pattern was described. With two example calculations, the method was explained in detail. The results of both examples show that the force field in liquid metal can be divided into several regions with different force features. Example 1 shows the effect of coil position on the evolution of the force field pattern in liquid metal. Example 2 is a kind of stirring by the travelling magnetic field ,whose results present the sub-structures in metal and show that most of them have almost the same rotating direction.
基金Supported by the Science Foundation of Shanghai Municipal Commission of Scienceand Technology!( 97JC1 41 0 7)
文摘The particle migrating behavior at solidifying front is discussed in theory with the application of electromagnetic force field(EMFF), on the basis of foregone analysis of force upon particle ahead of solidifying front without electromagnetic force field. The critical solidification velocities of particle pushing/engulfment transition ahead of horizontal and vertical interface are derived respectively when a certain EMFF is applied. And the critical electromagnetic forces of particle pushing/engulfment transition ahead of horizontal and vertical interface are also derived separately when a certain solidifying velocity is given.
文摘A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane(PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave lens form a coaxial compound lens system. The plane-concave lens equipped with driving coils is installed directly above the PDMS lens surrounded by the annular magnet. When different currents are applied, the annular magnet moves up and down, driving the PDMS film to undergo elastic deformation, and then resulting in longitudinal movement of the PDMS lens. The position change of the PDMS lens changes the focal length of the compound lens system. To verify the feasibility and practicability of this design, a prototype of our compound lens system is fabricated in experiment. Our proposed compound lens shows that its zoom ability reaches 9.28 mm when the current ranges from -0.20 A to 0.21 A.
文摘The mathematical model of the solenoid valve under varying temperatures is constructed to investigate its performance and enhance heat dissipation balance.The relationship between temperature and electromagnetic force is determined.Electrothermal coupling simulation using COMSOL is conducted,optimizing the outer diameter and length structure parameters of the coil.It is established that the heat dissipation of the coil is influenced by its outer diameter.Subsequently,based on optimized coil structure parameters,an orthogonal experimental design method combined with Ansys Maxwell is employed for simulation solution analysis to study the impact of structural parameters such as length,position,front and rear angles of the magnetic barrier ring in the iron core,armature length,and through-hole size on electromagnetic force.Optimal structural parameters are identified.Results indicate a decrease in steady-state electromagnet temperature by 3-4℃,an increase in the initial electromagnetic force by 32.63%,and a rise in the maximum electromagnetic force by 27.10%.
文摘To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process, ANSYS software was used to simulate electromagnetic force field and fluid velocity field in the alloy melt in a crucible tube in three coils. In the first section of the paper, eletromagnetic force field and fluid velocity field caused by single coil were simulated. The result of this simulation gives an average velocity of 3.2 cm/s and it is called critical velocity because a fluid velocity over it will cause a fine and spherical structure of solid primary a in a semi-solid melt. And, from this result, a reasonable temperature of semi-solid of the alloy and an electrical current intensity were established. The electrical current intensity of the result of this simulation corresponded to the current intensity used in a practice experiment, in which the primary α was obviously refined and sphericized. Based on this simulation of single coil electromagnetic stirring, in the second section of the paper, eletromagnetic force field and fluid velocity field caused by three coils were simulated. The result of the simulation shows that, 1) there is a semi-solid zone of 32 mm from bottom of the crucible tube to the upper; 2) the electrical current intensities of three coils of 400 A, 600 A, and 400 A, which were set to top range, middle range and bottom range of the tube, respectively, were the optimum parameters of electromagnetic current intensity under the condition of this investigation; and 3) under effect of these electromagnetic current intensity, the fluid velocities of the melt in the tube were 6.3 cm/s in top range, 3.75 cm/s in middle range, and 3.9 cm/s in bottom range of it, respectively.
文摘The upper vertical stability (VS) feeder is a part connected to the upper VS coil by a welding joint. The function of the feeder is to transfer current and coolant water to the VS coil. A giant electron^agnetic force will be generated during normal operation by the current flowing in the VS coils, interacting with the external background field. The Lorentz force will induce Tresca stress in the feeder. The amplitudes of the magnetic field and Lorentz force along the conductor running direction have been calculated based on Maxwell's equations. To extract the Tresca stress in the feeder, a finite element model was created using the software ANSYS and an electromagnetic load was applied on the model. According to the analytical design, the stresses were classified and evaluated based on ASME. In order to reduce the Tresca stress, some optimization works have been done and the Tresca stress has had a significant reduction in the optimized model. This analytical work figured out the stress distribution in the feeder and checked the feasibility of the prototype design model. The ANSYS analysis results will provide a guidance for later improvement and fabrication.
文摘ELM (edge localized mode) coils are key components of ITER that suppress the edge localized mode phenomenon. A giant electromagnetic force is generated during normal operations by the current flowing in the ELM coils interacting with the external background field. The Lorentz force will induce Tresca stress in the ELM coils. If the load goes beyond the allowable threshold, the coils can hardly satisfy the safety requirements. The right-hand bottom corner was chosen to perform our electromagnetic analyses. Based on the Maxwell equation, the detailed magnetic field and Lorentz force were calculated. By use of the finite element software ANSYS, the Tresca stress was extracted and evaluated based on our analytical design. The present analysis aims to verify the feasibility of the current design. It can also serve as guidance for fabrication and structural optimization.
基金supported by the National Natural Science Foundation of China(11172322)
文摘Space electromagnetic docking technology, free of propellant and plume contamination, offers continuous, reversible and synchronous controllability, which is widely applied in the future routine on-orbit servicing missions. Due to the inherent nonlinearities, couplings and uncertainties of an electromagnetic force model, the dynamics and control problems of them are difficult. A new modeling approach for relative motion dynamics with intersatellite force is proposed. To resolve these control problems better, a novel nonlinear control method for soft space electro-magnetic docking is proposed, which combines merits of artificial potential function method, Lyapunov theory and extended state observer. In addition, the angular momentum management problem of space electromagnetic docking and approaches of handling it by exploiting the Earth's magnetic torque are investigated. Finally, nonlinear simulation results demonstrate the feasibility of the dynamic model and the novel nonlinear control method.
文摘In this paper,the effects of Lorentz force on drag reduction for a circular cylinder have been studied experimentally and numerically.Based on its effects on drag reduction,the Lorentz force is found to be classified into two parts:one acts directly on the cylinder,named as the wall Lorentz force,and the other called the field Lorentz force acts on the fluid inside the boundary layer.The wall Lorentz force leads to the generation of a thrust,whereas the field Lorentz force results in drag increase.Since the former dominates the drag variation,the drag would reduce accordingly and even turn into negative (thrust) with the application of Lorentz force.
基金supported by the National Key R&D Program of China(Grant No.2023YFB4302500)。
文摘The operating speed of the commercial electromagnetic suspension(EMS)maglev train has been over 430 km/h,making it the fastest means of land transportation.With the increasing demands of people traveling,it is necessary to further improve the operating speed of maglev trains.Aiming to examine whether the existing EMS system can meet the requirements of ultra-highspeed operation(more than 600 km/h),the electromagnetic characteristics of an EMS linear motor under the operating speed of 600–1000 km/h fed by a square-wave voltage supply is investigated in this article.First,an electromagnetic field model of the EMS system under the square-wave voltage supply is established to investigate its electromagnetic performance,e.g.,the characteristics of phase current,the magnetic flux density,and the electromagnetic force.Second,the relationship between the harmonic components of the air-gap magnetic flux density and electromagnetic force is investigated using the two-dimensional fast Fourier transform(2D-FFT)to reveal the mechanism of electromagnetic force ripple.Third,to address the issues of excessive armature current density and significant electromagnetic force ripple,the linear motor is re-designed by enlarging the stator slot area and reshaping the mover's main magnetic poles.Furthermore,the Taguchi method is used to further improve the electromagnetic characteristics of the linear electric motor.Finally,the effectiveness of the proposed optimal design is validated by the finite-element analysis(FEA)based co-simulation.
基金Project supported by the National Natural Science Foundation of China(No.10472069).
文摘Some of the previous theories in the electrostrictive and magnetostrictive materials and their differences are discussed in this paper. A variational principle in the general thermodynamic sense is given and the governing equations can be derived from this principle. Illustrational examples are given.
文摘A three-dimensional (3-D) transient model has been developed to investigate plasma deformation driven by a magnetic field and its influence on arc stability in a circuit breaker. The 3-D distribution of electric current density is obtained from a current continuity equation along with the generalized Ohm's law; while the magnetic field induced by the current flowing through the arc column is calculated by the magnetic vector potential equation. When gas interacts with an arc column, fundamental factors, such as Ampere's law, Ohm's law, the turbulence model, transport equations of mass, momentum and energy of plasma flow, have to be coupled for aria- lyzing the phenomenon. The coupled interactions between arc and plasma flow are described in the fl'amework of time-dependent magnetohydrodynamic (MHD) equations in conjunction with a K-~ turbulence model. Simulations have been focused on sausage and kink instabilities in plasma (these phenomena are related tO pinch effects and electromagnetic fields). The 3-D sjm- ulation reveals the relation between plasma deformation and instability phenomena, which affect arc stability during circuit breaker operation. Plasma deformation is the consequence of coupled interactions between the electromagnetic force and plasma flow described in simulations.
基金This work was supported by the National Natural Science Foundation of China(Nos.61772242,61402204,61572239)Research Fund for Advanced Talents of Jiangsu University(No.14JDG141)+2 种基金Science and Technology Project of Zhenjiang City(No.SH20140110)Special Software Development Foundation of Zhenjiang City(No.201322)Science and Technology Support Foundation of Zhenjiang City(Industrial)(No.GY2014013).
文摘Most image segmentation methods based on clustering algorithms use singleobjective function to implement image segmentation.To avoid the defect,this paper proposes a new image segmentation method based on a multi-objective particle swarm optimization(PSO)clustering algorithm.This unsupervised algorithm not only offers a new similarity computing approach based on electromagnetic forces,but also obtains the proper number of clusters which is determined by scale-space theory.It is experimentally demonstrated that the applicability and effectiveness of the proposed multi-objective PSO clustering algorithm.
基金This project is supported by the National Natural Science Foundation of China (Grant No. 59734080) the Plan of National Fundamental Research Development of China (Grant No. G1998061510).
文摘A coupled model including electromagnetic field, fluid dynamic, heat transfer and solidification, is developed and applied to the numerical simulation of steel flow and solidification in a 100mm × 100mm soft-contact mold. In this study, the 3D finite difference method and non-staggered grid system for fluid flow with body fitted coordinate were employed. Numerical results show that the electromagnetic force mainly affects the steel flow at upper part of mold, especially in the vicinity of meniscus. There exist upward flows covering the surfaces of the billet due to the concentration of electromagnetic force on the upper part of the billet. This flows join together and form a downward flow near the SEN, so a distinct circulating flow zone is formed at upper part of mold. After applying electromagnetic force, the steel velocity is improved and the temperature is raised. The strong stirring of electromagnetic force on liquid steel makes the kinetic energy on free surface increase. It is clearly seen that the solidification start point shifts downward in soft contact mold. As a result, the initial shell thickness gets thin and the initial solidification shell length is shortened.