U-shaped Electromagnet Research Articles

A comparative analysis on the single-phase and two-phase mixture models for calculation of ferrofluid convective heat transfer in the presence of a magnetic field: a numerical study

PurposeThis paper aims to analyze the accuracy of the single and two-phase numerical methods for calculation of ferrofluid convective heat transfer in the presence of a magnetic field. The findings of current study are compared with previous single-phase numerical results and experimental data. Accordingly, the effect of various parameters including nanoparticles concentration, Reynolds number and magnetic field strength on the performance of the single and two-phase models are evaluated.Design/methodology/approachA two-phase mixture numerical study is carried out to investigate the influence of four U-shaped electromagnets on the hydrodynamic and thermal characteristics of Fe3O4/Water ferrofluid flowing inside a heated channel.FindingsIt is observed that the applied external magnetic field signifies the convective heat transfer from the channel surface, despite local reduction at a few locations. The maximum heat transfer enhancement is predicted as 23% and 25% using single and two-phase models, respectively. The difference between the results of the two models is mainly attributed to the slip velocity effect which is accounted for in the two-phase model. The magnetic field gradient leads to a significant increase in the slip velocity which in turn causes a slight difference in velocity and temperature profiles obtained by the single and two-phase models in the magnetic field region. According to percentage error calculation, the two-phase method is generally more accurate than the single-phase method. However, the percentage error of both models improves by decreasing either magnetic field intensity or Reynolds number.Originality/valueFor the first time in the literature, to the best of the authors’ knowledge, the current work analyzes the accuracy of the single and two phase numerical methods for calculation of ferrofluid convective heat transfer in the presence of a magnetic field.

Application of coercimetry to assess the functional properties of materials

The purpose of this work is a comparative study of the possibilities of various types of coercimeters to assess the functional properties of ferromagnetic materials. Conducted research have shown that the limitation of the maximum measured value of the coercive force using an attached transducer with a U-shaped electromagnet is due to the lower value of the magnetic resistance of the tested workpiece. The upper limit of measurements of the coercive force using a two-pole transducer is determined by the magnitude of the tangential component of the magnetic field only by the possibility of magnetizing the tested object.

A novel magnetorheological elastomer-based adaptive tuned vibration absorber: design, analysis and experimental characterization

The present study aims at the development of a novel semi-active adaptive tuned vibration absorber (SATVA) capable of tuning its natural frequency adaptively in low frequency range. The absorber consists of a multilayer sandwich beam featuring magnetorheological elastomer (MRE) and integrated U-shaped electromagnets which are attached at the top and bottom layers of the sandwich beam. Electromagnets are designed to provide the required magnetic field to alter the stiffness of the MRE layers while also acting as the active mass of the absorber. Based on the characterization of the shear and loss modulus of the fabricated MRE samples, the finite element (FE) model of the proposed SATVA has been developed to analyze the absorber to meet the design requirements and also to evaluate its dynamic performance. The proposed SATVA is then fabricated and experimental set-ups are designed to validate the electromagnet and FE models. The frequency response function of the proposed SATVA is then investigated under different levels of the applied current to the electromagnets. It has been shown that good agreement exists between simulation and FE results. A frequency-shift of approximately 9% was achieved while maintaining a reasonable factor of safety for material constraints. Finally, using the validated FE mode, a parametric study has been conducted to investigate the effect of different design parameters.

Multidisciplinary Design Optimization of a Novel Sandwich Beam-Based Adaptive Tuned Vibration Absorber Featuring Magnetorheological Elastomer.

The present study aims to investigate the dynamic performance and design optimization of a novel magnetorheological elastomer based adaptive tuned vibration absorber (MRE-ATVA). The proposed MRE-ATVA consists of a light-weight sandwich beam treated with an MRE core layer and two electromagnets installed at both free ends. Three different design configurations for electromagnets are proposed. The finite element (FE) model of the proposed MRE-ATVA and magnetic model of the electromagnets are developed and combined to evaluate the frequency range of the absorber under varying magnetic field intensity. The results of the developed model are validated in multiple stages with available analytical and simulation data. A multidisciplinary design optimization strategy has been formulated to maximize the frequency range of the proposed MRE-based ATVA while respecting constraints of weight, size, mechanical stress, and sandwich beam deflection. The optimal solution is obtained and compared for the three proposed ATVA configurations. The optimal ATVA with a U-shaped electromagnet shows more than 40% increase in the natural frequency while having a total mass of 596 g.

Coercimetry with Magnetization by a U-Shaped Electromagnet

A method is proposed for measuring the coercive force using a U-shaped electromagnet with a gap between the electromagnet poles and the test sample. It is demonstrated that the device can operate in a dynamic mode under pulsed magnetization reversal. Numerical simulation and experimental results are compared.

On modeling on a single-winding forced valve electromagnet in a circuit with a ballast resistor

We have built a mathematical model of starting up a forced U-shaped valve electromagnet of static voltage taking into account dynamic parameters and characteristics. The offered model takes into account the influence of eddy currents in the closed circuits of the magnetic system. At the first stage we have developed a mathematical model that allows to determine optimum dimensions, to minimize the mass of active materials (the total mass of copper for windings and ferromagnetic steel), that are used in construction of the electromagnet. Then, based on a known method of integration of the dynamic equations we have obtained an actuation model of the valve magnet taking onto account equivalent resistances of cores of both circular and rectangular cross-sections. Modeling of dynamic parameters and characteristics was done taking into account secondary con-tours without increasing order of differential equations. We list calculated values of dynamic parameters and characteristics of the electromagnet in a circuit with a balance resistor.

Modelling of magnetic field and flux in objects having surface-hardening and transition layer

A finite element simulation of the distribution of the magnetic field and flux in locally magnetized steel objects subjected to surface hardening and having after hardening a three-layer structure: a hardened surface layer, a transition layer, an unstressed core; has been conducted. Magnetization of the tested object was conducted using a U-shaped electromagnet. As a result, pictures of the distribution of the magnetic field in the monitoring object were obtained. The values of induction depending on the depth of the hardened layer for a fixed transition layer at different points of space relative to the surface of the object of control are obtained.

Magnetic flux distribution in a ferromagnetic material magnetized by U-shaped electromagnets of different geometric dimensions types

A model experiment has been carried out on studying the type of changes in the magnetic induction in a homogeneous isotropic sample that is locally magnetized with attached U-type electromagnets of different geometrical dimensions. The study was aimed at finding out magnetic flux distribution at different locations within the sample and determining the effect that the geometry of attached electromagnets has on this distribution.

Characteristis of Magnetic Barkhausen Noise with U-shaped Electromagnet Magnetizer

Characteristis of Magnetic Barkhausen Noise with U-shaped Electromagnet Magnetizer

Yaw Motion Control of Electromagnetic Guidance System for High-Speed Maglev Vehicles

In an attractive-type high-speed magnetic levitation (maglev) train, separate electromagnets are used for lateral guidance. For the guidance system, a U-shaped electromagnet that uses transverse flux has been designed and analyzed. Electromagnets counterbalance centrifugal forces during curving as well as under all operating conditions so that the clearances between on-board magnets and the guideway surface can be maintained within an allowable range. Because of the rigidity of the bogie, coupling effects exist among the magnets that are controlled independently. This study incorporates bogie yaw motion into control law for adjusting the voltages applied to magnets to provide constant clearance control. The effects of bogie yaw motion on guidance control performance are investigated experimentally using a full-scale vehicle.

An electromagnetic–acoustic transducer with pulsed biasing

Pulsed magnetizing systems of EMA transducers with a tangential biasing field with respect to the surface of a test object are considered. A method for calculating the parameters of a U-shaped pulsed electromagnet, which can produce strong magnetic fields in the material of a test object and allows the efficiency of exciting and receiving ultrasonic waves by the EMA method to be increased, is presented. As an example, the parameters of a U-shaped electromagnet are calculated for an EMA transducer that excites Lamb and Rayleigh waves.

Hybrid Reluctance Machines with U-Shaped Electromagnets and Permanent Magnets

This paper is about hybrid reluctance machines, in which the stator or fixed part has a combination of U-shaped electromagnets with permanents magnets placed between their arms while the moving part is simply a structure with salient poles. They can be designed to build different types of rotary or linear electric motors and generators with outstanding performances. In this paper, first, the principle of operation of these machines is explained. Then different types of hybrid reluctance machines using this particular structural configuration are described showing their potential based on simulations and experimental results.

The topography of the field and flux inside and above the surfaces of ferromagnetic plates during their contact and contactless magnetization

Modeling and experimental studies of the spatial distributions of the field and flux inside and above the surface of ferromagnetic plates of different dimension types, which were locally magnetized by U-shaped electromagnets, were performed. It was established that the location of a magnetic inhomogeneity in the interpole zone of an electromagnet substantially affects the results of a local measurement of the coercive force using a demagnetization current. It is shown that the presence of a gap in the magnetic circuit impairs the magnetization of the interpole zone of an object to a higher degree than the magnetization of the near-pole zone. Recommendations on the concentration of the magnetic flux in the interpole zone via a decrease in the interpole distance of the electromagnet are given. Possible locations of internal-field probes that provide local measurements of the magnetic properties of a substance are determined.

Development of a 3-DOF Mobile Positioning Mechanism with 6 Contact Points (Input Voltages by Dynamic Analysis under Conditions of Quasi-Constant Internal Forces)

In this paper, we describe a design and input voltage waveforms for a 3-DOF precise inchworm mechanism with 6 contact points. In those ten years, we have developed an omnidirectional and holonomic inchworm mechanism to provide a flexible, compact, and precise microscopic processing. In previous mechanism, a pair of U-shaped electromagnets arranged to cross each other are connected by four piezoelectric actuators so that the mechanism can move in any direction. However, microscopic operations are still difficult because of vibrations caused by inclination of the U-shape electromagnets. In this paper, we have proposed newly developed mechanism composed of a pair of Y-shaped electromagnets and six piezoelectric actuators to prevent the inclination of the electromagnets. We have analyzed a 3-DOF simple vibration model to get the dynamical response of the mechanism. We have also solved quasi-constant conditions of internal forces between a pair of the Y-shaped-electromagnets. Finally, we develop the expression for input voltage waveforms which represents holonomic and omnidirectional motion. We have checked the validity of the theoretical input voltages by orthogonal and rotational experimental results.

U 자형 전자석을 사용하는 자기부상열차의 횡진동 저감 연구

도시형 자기부상열차는 U 자형 전자석만을 사용하여 부상공극을 일정하게 유지하며 주행한다. U자형 전자석은 그 형상 특성으로 인하여 전자석 위치에 따라 안내력을 동시에 갖기 때문에 능동적 횡공극 제어가 없이도 차량을 레일에 따라 안내할 수 있는 장점을 갖는다. 그러나 횡공극을 제어하기 않기 때문에 횡진동이 증가하여 승차감 및 주행안정성에 악영향을 미칠 수 있다. 본 논문에서는 능동제어가 없이도 횡진동을 저감시키기 위한 방법으로 횡댐퍼 적용 효과에 대한 분석이 이루어진다. 이를 위하여 자기부상열차의 횡방향 고유진동특성을 우선 해석하고, 횡방향 댐퍼를 설치했을 때의 진동저감 효과 분석이 이루어진다. 정확한 횡진동 예측을 위하여 자기부상열차의 3 차원 다물체 동역학 모델을 사용하였다. 본 논문의 결과를 통해서 자기부상열차의 횡진동 저감을 위한 횡댐퍼 채택 제안에 활용하고자 한다.

Development of a 3-DOF Mobile Positioning Mechanism with 6 Contact Points

In this paper, we describe the design, development and experimental results of a 3-DOF precise inchworm mechanism with six contact points. During the last ten years, we have developed an omnidirectional and holonomic inchworm mechanism to provide flexible, compact, and precise microscopic processing. In a previous mechanism, four piezoelectric actuators connected a pair of U-shaped electromagnets arranged to cross each other so that the mechanism can move precisely in any direction. However, positioning repeatability was made difficult by an inclination of the U-shaped electromagnets. Therefore, we designed a new omnidirectional inchworm mechanism composed of a pair of Y-shaped electromagnets and six piezoelectric actuators to prevent the inclination of the electromagnets. In addition, we explain the drive principle of the newly developed mechanism. Finally, we show the experimental results of the positioning repeatability of translational motions in four directions with a payload.

Levitation force analysis of medium and low speed maglev vehicles

The rule of levitation force variation with different structure and electromagnetic parameters provides a basis for electromagnet design of electromagnetic suspension (EMS) medium and low speed maglev vehicles. In order to acquire accurate calculation results of levitation force, different calculation methods, including analytical method, 2D FEM (finite element method), and 3D FEM, are applied to investigate the impact of various structural parameters, such as excitation current, air gap, lateral offset, and pole width, on levitation force. The analytical analysis is based on the classic mathematical model of levitation force between electromagnet and rail and performed with MATLAB. In the 2D and 3D FEMs, the numerical calculation of the levitation force is conducted with Ansoft by taking the magnetic saturation into account. In addition, the longitudinal end effect on the levitation force calculation is considered in the 3D FEM. The results show that the 3D FEM is the most accurate among the above three methods for calculating the levitation force, and the analytical method can only work for small current and/or large air gap conditions. A lateraloffset between vehicle and rail will reduce the levitation force; the levitation force descends sharply once the lateral offset exceeds the threshold, i.e., 8% of the pole width for U-shaped electromagnets. The maximum lift-to-weight ratio emerges when the pole width ratio of F type rail to electromagnet is 6:7. This may offer a reference for EMS maglev vehicle design and application.

Distribution of the induction of a quasi-stationary magnetic field created in a ferromagnet by an attachable electromagnet

As a result of numerical calculations, the spatial and time distributions of the induction of a quasi-stationary magnetic field, which was created in a studied ferromagnet by U-shaped and solenoidal attachable electromagnets (AEMs) at frequencies of 1 and 10 Hz, were obtained. The presence of a phase shift between the amplitude values of the magnetic-field induction at different depths in the specimen, which increases with the frequency of the exciting current, was revealed. The dependences of the magnetic-field penetration depth into the ferromagnet on the magnetic reversal frequency were studied. It was found that for the frequency range under study the magnetic-field penetration depth for both types of AEM is smaller than that for the corresponding stationary case.

Simulation of field and inductance spatial distribution in locally magnetized massive objects and optimization of U-shaped transducer design

The field and magnetic-inductance spatial distributions in plates that differ in geometric dimensions and magnetic properties, which were magnetized locally by U-shaped electromagnets of different standard sizes, were calculated using the finite element method. The magnetic-flux side scattering, which impedes the magnetization, was estimated qualitatively. Recommendations on designing magnetizing instruments, which are characterized by low side scattering, are given.

Curving performance simulation of an EMS-type Maglev vehicle

For electromagnetic suspension (EMS) type urban Maglev vehicles using a U-shaped electromagnet, the levitation and guidance forces are generated by only one electromagnet. Although the levitation force is actively controlled by changing the voltage of the electromagnet, the guidance force is passively determined by the levitation force. In addition, the curve negotiation performance of EMS-type urban Maglev vehicles using a U-shaped electromagnet must be considered, because an urban guideway may have some curves with shorter radii. It is, therefore, necessary to predict the curving performance with the greatest accuracy possible, in order to improve electromagnetic suspension and establish guideway design specifications. The objective is to establish a new dynamic modelling technique, so as to achieve more realistic curving simulation and thus to more accurately evaluate the curving performance of an EMS-type Maglev vehicle. The use of a full vehicle multibody dynamic model is proposed, and is applied to the evaluation of curving performance. Design changes are also investigated to obtain the bogie design directions for minimising variation in the lateral air gap, which is a criterion for curving performance.