Design of Magnetic Circuit for Stationary Plasma Thruster

Abstract SPT-100 electrostatic thruster is considered, and the effects of magnetic circuit is studied by introducing magnetic screen. The magnetic flux density in the discharge channel is generated with the help of one inner coil and four outer coils. The radial magnetic field has to be maximum near the exit plane of the thruster to trap the electrons in acceleration region which are emitted from an external hollow cathode. These electrons help in increasing the ionization rate of the propellant gas. This is obtained by placing magnetic poles near exit plane. It helps to traps the electrons emitted from the external hollow cathode. The magnetic circuit should be designed such that the magnetic flux density is near to zero at the anode plane to reduce interaction of electrons with channel walls. To arrive at such better design, magnetic screens are used. Computational simulations are performed to quantify the magnetic flux density distribution along the channel using COMSOL Multiphysics software. The simulation results show that the obtained radial magnetic flux density is maximum near the exit plane, and the magnetic screens help in reducing the magnetic field at the anode region while maintaining the maximum magnetic field at the exit plane.

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A Mathematical Model of a Modified Voice Coil Energy Harvester

Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B ◽

10.1115/imece2011-64354 ◽

2011 ◽

Author(s):

Alireza Hekmati ◽

Siamak Arzanpour

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Flux Density ◽

Peak Power ◽

Magnetic Field Intensity ◽

Magnetic Circuit ◽

Magnetic Flux Density ◽

Magnetic Conductor ◽

Magnetic Circuits ◽

The Magnetic Field

This paper presents a mathematical modeling of a modified voice coil generator, which consists of a moving coil within a fixed magnetic circuit. The simulation has been done with Comsol Multiphysics software, which is a powerful tool to demonstrate the pattern of magnetic field and calculate the induced current in the coil. In our simulations, the magnetic circuit consists of the magnetic conductor and the air gap. In this analysis, the magnetic flux density and the magnetic field intensity are calculated. Moreover, through calculation of the total reluctance of the magnetic circuit and employing the ohm’s law for magnetic circuits, the effect of the length and cross section of the total circuit on the magnetic flux are investigated. Finally, a pattern for the magnetic flux density are demonstrated and the simulation result indicates that the magnetic field is well concentrated on the coil area, therefore this prototype can capture and convert most of the kinetic energy to electricity. A prototype has been fabricated and tested on the shaker. The experimental results indicate that this setup is able to produce the maximum voltage of 0.326 V and the peak power equal to 2.605 mW in 35 Hz frequency and 1 mm peak to peak amplitude.

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Characterization and modeling of hard magnetic particle–based magnetorheological elastomers

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x20942569 ◽

2020 ◽

pp. 1045389X2094256

Author(s):

Nader Mohseni Ardehali ◽

Masoud Hemmatian ◽

Ramin Sedaghati

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Flux Density ◽

Magnetic Particle ◽

Excitation Frequency ◽

Viscoelastic Behavior ◽

Magnetic Flux Density ◽

Driving Frequency ◽

Magnetorheological Elastomers ◽

Magnetic Poles

Hard magnetic particle–based magnetorheological elastomers are novel magnetoactive materials in which, unlike the soft particle–based magnetorheological elastomers, the particles provide magnetic poles inside the elastomeric medium. Therefore, the stiffness of the hard magnetic particle–based magnetorheological elastomers can be increased or decreased by applying the magnetic field in the same or opposite direction as the magnetic poles, respectively. In the present work, the viscoelastic properties of hard magnetic particle–based magnetorheological elastomers operating in shear mode have been experimentally characterized. For this purpose, hard magnetic particle–based magnetorheological elastomers with 15% volume fraction of NdFeB magnetic particles have been fabricated and then tested under oscillatory shear motion advanced rotational magneto-rheometer to investigate their viscoelastic behavior under varying excitation frequency and magnetic flux density. The influence of the shear strain amplitude and driving frequency is examined under various levels of applied magnetic field ranging from −0.2 to 1.0 T. Finally, a field-dependent phenomenological model has been proposed to predict the variation of storage and loss moduli of hard magnetic particle–based magnetorheological elastomers under varying excitation frequency and applied magnetic flux density. The results show that the proposed model can accurately predict the viscoelastic behavior of hard magnetic particle–based magnetorheological elastomers under various working conditions.

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The Innovative Design of Deep In Situ Pressure Retained Coring Based on Magnetic Field Trigger Controller

Advances in Civil Engineering ◽

10.1155/2020/8873628 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Guikang Liu ◽

Mingzhong Gao ◽

Zhiwen Yang ◽

Ling Chen ◽

Maoquan Fu ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Flux Density ◽

Magnetic Force ◽

Magnetic Circuit ◽

Minimum Condition ◽

Magnetic Flux Density ◽

Valve Seat ◽

Deep Rock

Deep rock mass theory has not yet been completely established, which leads to a lack of theoretical guidance for deep resource development and poor continuity among engineering activities. The foundation of deep rock mechanics theory is to achieve the deep in situ rock fidelity coring (including the retaining of the pore pressure and temperature). To realize this, pressure-retaining coring technology is required. A self-triggered pressure-retaining controller based on magnetic control is proposed in this paper. The pressure-retaining controller realizes pressure-retaining coring in any direction by triggering the closure of the valve cover by a magnetic force, forming a magnetic seal. Fifteen combined magnetic circuit design schemes are proposed. The magnetic flux density norm distribution and magnetic force evolution law of different schemes are then quantitatively analyzed by the finite element method. The results show that a complex magnetization combination can weaken the nonlinear negative correlation between the magnetic force and distance. The optimal design of the valve seat magnetic circuit is Scheme 9, with the valve seat consisting of four shape identical tile magnets. Among the schemes, for Scheme 9, the magnetic flux density norm of the valve cover is the most concentrated. The maximum magnetic flux density norm is in the middle, and the magnetic force at 35 mm from the valve cover to the valve seat is 2.915 N. Scheme 9 satisfies the minimum condition of the mechanical model and verifies the feasibility of magnetic field triggering. This research can be used to gain a better understanding of deep Earth properties and provides technology for the improved design of deep in situ pressure-retaining coring devices.

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Design of a New 1D Halbach Magnet Array with Good Sinusoidal Magnetic Field by Analyzing the Curved Surface

Sensors ◽

10.3390/s21072522 ◽

2021 ◽

Vol 21 (7) ◽

pp. 2522

Author(s):

Guangdou Liu ◽

Shiqin Hou ◽

Xingping Xu ◽

Wensheng Xiao

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Permanent Magnet ◽

Flux Density ◽

Permanent Magnets ◽

Air Gap ◽

Curved Surface ◽

Magnetic Flux Density ◽

Sinusoidal Magnetic Field ◽

The Magnetic Field

In the linear and planar motors, the 1D Halbach magnet array is extensively used. The sinusoidal property of the magnetic field deteriorates by analyzing the magnetic field at a small air gap. Therefore, a new 1D Halbach magnet array is proposed, in which the permanent magnet with a curved surface is applied. Based on the superposition of principle and Fourier series, the magnetic flux density distribution is derived. The optimized curved surface is obtained and fitted by a polynomial. The sinusoidal magnetic field is verified by comparing it with the magnetic flux density of the finite element model. Through the analysis of different dimensions of the permanent magnet array, the optimization result has good applicability. The force ripple can be significantly reduced by the new magnet array. The effect on the mass and air gap is investigated compared with a conventional magnet array with rectangular permanent magnets. In conclusion, the new magnet array design has the scalability to be extended to various sizes of motor and is especially suitable for small air gap applications.

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Effects of External Transverse Alternating Magnetic Field on the Oscillating Amplitude of Atmospheric Pressure Plasma Arc

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.129-131.692 ◽

2010 ◽

Vol 129-131 ◽

pp. 692-696

Author(s):

Jian Bing Meng ◽

Xiao Juan Dong ◽

Chang Ning Ma

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Flux Density ◽

Flow Rate ◽

Gas Flow ◽

Atmospheric Pressure Plasma ◽

Alternating Magnetic Field ◽

Magnetic Flux Density ◽

Plasma Arc ◽

Arc Current

A mathematical model was developed to describe the oscillating amplitude of the plasma arc injected transverse to an external transverse alternating magnetic field. The characteristic of plasma arc under the external transverse alternating magnetic field imposed perpendicular to the plasma current was discussed. The effect of processing parameters, such as flow rate of working gas, arc current, magnetic flux density and the standoff from the nozzle to the workpiece, on the oscillation of plasma arc were also analyzed. The results show that it is feasible to adjust the shape of the plasma arc by the transverse alternating magnetic field, which expands the region of plasma arc thermal treatment upon the workpiece. Furthermore, the oscillating amplitude of plasma arc decreases with decrease of the magnetic flux density. Under the same magnetic flux density, more gas flow rate, more arc current, and less standoff cause the oscillating amplitude to decrease. The researches have provided a deeper understanding of adjusting of plasma arc characteristics.

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FFC NMR Relaxometer with Magnetic Flux Density Control

Journal of Low Power Electronics and Applications ◽

10.3390/jlpea9030022 ◽

2019 ◽

Vol 9 (3) ◽

pp. 22

Author(s):

António Roque ◽

Duarte M. Sousa ◽

Pedro Sebastião ◽

Elmano Margato ◽

Gil Marques

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Flux Density ◽

Low Cost ◽

Current Control ◽

Magnetic Flux Density ◽

Density Control ◽

Earth Magnetic Field ◽

Innovative Solution ◽

Field Cycling

This paper describes an innovative solution for the power supply of a fast field cycling (FFC) nuclear magnetic resonance (NMR) spectrometer considering its low power consumption, portability and low cost. In FFC cores, the magnetic flux density must be controlled in order to perform magnetic flux density cycles with short transients, while maintaining the magnetic flux density levels with high accuracy and homogeneity. Typical solutions in the FFC NMR literature use current control to get the required magnetic flux density cycles, which correspond to an indirect magnetic flux density control. The main feature of this new relaxometer is the direct control of the magnetic flux density instead of the magnet current, in contrast with other equipment available in the market. This feature is a great progress because it improves the performance. With this solution it is possible to compensate magnetic field disturbances and parasitic magnetic fields guaranteeing, among other possibilities, a field control below the earth magnetic field. Experimental results validating the developed solution and illustrating the real operation of this type of equipment are shown.

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PDMS Membrane Microactuator for Focal Tunable Microlens

Microelectromechanical Systems ◽

10.1115/imece2006-14278 ◽

2006 ◽

Author(s):

Seok Woo Lee ◽

Seung S. Lee

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Flux Density ◽

Lorentz Force ◽

Spin Coating ◽

Large Displacement ◽

Pdms Membrane ◽

Magnetic Flux Density ◽

Optical Performance ◽

Electrical Components

In this paper, PDMS membrane for a large displacement is fabricated by new fabrication process which can be integrated with electrical components on substrates fabricated by conventional microfabrication processes and the performance of the membrane using electromagnetism was evaluated. Rectangular PDMS membranes are designed as 2mm and 3mm in width, respectively and are actuated by Lorentz force induced by current paths spread on the membrane. The PDMS membrane is fabricated by reducing a viscosity of uncured PDMS with dilution and spin coating on the substrate on which electric components generating Lorentz force. Finally, PDMS membrane including electric components is opened by a bulk micromachining. The device is tested in magnetic field induced by Nd-Fe-B magnet whose magnetic flux density is 90G. When applied currents are 20, 25, and 30mA, the maximum deflections of membranes are 1.21, 3.07, and 20.2μm for 1.5mm width membrane and 3.34, 31.0, and 50.9μm for width 3mm membrane, respectively. The large displacement PDMS membrane actuator has potentially various applications such as fluidics, optics, acoustics, and electronics. Currently, we are planning to measure the optical performance of the actuator as a focal tunable liquid lens.

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Platform Design for Characterizing Shear Force Produced by Magnetized Magnetorheological Fluid

ASME 2019 28th Conference on Information Storage and Processing Systems ◽

10.1115/isps2019-7450 ◽

2019 ◽

Author(s):

Ping-Hsun Lee ◽

Jen-Yuan (James) Chang

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Yield Stress ◽

Flux Density ◽

Shear Force ◽

Permanent Magnets ◽

Magnetic Flux Density ◽

Finite Element Method Result ◽

Mr Fluid ◽

The Magnetic Field

Abstract In this paper we proposed a platform for measuring shear force of magnetorheological (MR) fluid by which the relationship of yield stress and magnetic flux density of specific material can be determined. The device consisted of a rotatable center tube in a frame body and the magnetic field was provided by two blocks of permanent magnets placed oppositely outside the frame body. The magnitude and direction of the magnetic field were manipulated by changing the distance of the two permanent magnets from the frame body and rotating the center tube, respectively. For determining the magnetic field of the device, we adopted an effective method by fitting the FEM (finite element method) result to the measured one and then rebuilt the absent components to approximate the magnetic field, which was hardly to be measured simultaneously as different device setup were required. With the proposed platform and analytical methods, the drawing shear force and the corresponding yield stress contributed by MR fluid could be evaluated in respect to the magnitude and direction of given magnetic flux density with acceptable accuracy for specific designing purposes without a large, complex, and expensive instrument.

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