Turbulent duct flows in a liquid metal magnetohydrodynamic power generator

2012 ◽  
Vol 713 ◽  
pp. 243-270 ◽  
Author(s):  
Hiromichi Kobayashi ◽  
Hiroki Shionoya ◽  
Yoshihiro Okuno
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Load Resistance ◽  
High Load ◽  
Magnetic Flux Density ◽  
Load Factor ◽  
Mean Velocity ◽  
Power Generator ◽  
Optimal Load ◽  
The Magnetic Field

AbstractWe numerically assess the influence of non-uniform magnetic flux density and connected load resistance on turbulent duct flows in a liquid metal magnetohydrodynamic (MHD) electrical power generator. When increasing the magnetic flux density (or Hartmann number), an M-shaped velocity profile develops in the plane perpendicular to the magnetic field; the maximum velocity in the sidewall layer of the M-shaped profile increases to maintain the flow rate. Under the conditions of a relaminarized flow, the turbulence structures align along the magnetic field and flow repeatedly like a von Kármán vortex sheet. At higher Hartmann numbers, the wall-shear stress in the sidewall layer increases and the sidewall jets transit to turbulence. The sidewall jets in the MHD turbulent duct flows have profiles similar to the non-MHD wall jets, i.e. a mean velocity profile with outer scaling, Reynolds shear stress with the opposite sign in a sidewall jet, and two maxima for the turbulent intensities in a sidewall jet. The Lorentz force suppresses the vortices of the secondary mean flow near the Hartmann layer for low Hartmann numbers, whereas the secondary vortices remain near the Hartmann layer for high Hartmann numbers. An optimal load resistance (or load factor) to obtain a maximum electrical efficiency exists, because the strong Lorentz force for a low load factor and unextracted eddy currents for a high load factor reduce efficiency. When the value of the load factor is changed, the profiles of mean velocity and r.m.s. for the optimal load factor produce almost the same profiles as the high load factor near the open-circuit condition.

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

Sensors ◽  
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.

scholarly journals Calculation of Transient Magnetic Field and Induced Voltage in Photovoltaic Bracket System during a Lightning Stroke

2021 ◽  
Vol 11 (10) ◽  
pp. 4567
Author(s):  
Xiaoqing Zhang ◽  
Yaowu Wang
Keyword(s):  
Magnetic Field ◽  
Time Derivative ◽  
Equivalent Circuit Model ◽  
Magnetic Flux Density ◽  
Induced Voltage ◽  
Lightning Stroke ◽  
Transient Magnetic Field ◽  
Lightning Current ◽  
Time Space ◽  
The Magnetic Field

An effective method is proposed in this paper for calculating the transient magnetic field and induced voltage in the photovoltaic bracket system under lightning stroke. Considering the need for the lightning current responses on various branches of the photovoltaic bracket system, a brief outline is given to the equivalent circuit model of the photovoltaic bracket system. The analytic formulas of the transient magnetic field are derived from the vector potential for the tilted, vertical and horizontal branches in the photovoltaic bracket system. With a time–space discretization scheme put forward for theses formulas, the magnetic field distribution in an assigned spatial domain is determined on the basis of the lightning current responses. The magnetic linkage passing through a conductor loop is evaluated by the surface integral of the magnetic flux density and the induced voltage is obtained from the time derivative of the magnetic linkage. In order to check the validity of the proposed method, an experiment is made on a reduced-scale photovoltaic bracket system. Then, the proposed method is applied to an actual photovoltaic bracket system. The calculations are performed for the magnetic field distributions and induced voltages under positive and negative lightning strokes.

Uticaj armirano betonskog stuba na raspodelu magnetskog polja mešovitog voda

2020 ◽  
Vol 22 (1-2) ◽  
pp. 58-64
Author(s):  
Teodora Gavrilov ◽  
◽  
Karolina Kasaš-Lažetić ◽  
Kristian Haška ◽  
Miroslav Prša
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Magnetic Field Distribution ◽  
Magnetic Flux Density ◽  
Reinforcing Bars ◽  
Magnitude Distribution ◽  
Calculation Results ◽  
Mixed Power ◽  
The Impact ◽  
The Magnetic Field

In this paper, the analysis of magnetic field distribution of overhead mixed power line (20 kV/0.4 kV) supported by reinforced concrete towers, named MNL-12 is presented. The impact of ferromagnetic, conductive parts of the pylons (reinforcing bars, billets and cross arm beams) on magnetic field distribution is investigated. The numerical calculations were performed in COMSOL Multiphysics program package on simplified 2D model. The main goal of the calculations was to examine the impact of currents induced in ferromagnetic conductive parts on magnetic field produced by currents in the power system’s conductors. The calculation results are presented graphically, as the diagrams of the magnetic flux density magnitude distribution in the tower plan, normal to the system’s axe. The calculation results demonstrated that the magnetic field of induced currents decreases the magnetic field produced by the currents of overhead power system.

Investigation on the Improvement of Surface Quality by the Magnetic Plate-Assisted Magnetic Abrasive Finishing Process

2021 ◽  
Vol 1018 ◽  
pp. 111-116
Author(s):  
Yan Hua Zou ◽  
Hui Jun Xie
Keyword(s):  
Magnetic Field ◽  
Surface Quality ◽  
Field Distribution ◽  
Magnetic Field Distribution ◽  
Magnetic Flux Density ◽  
Magnetic Pole ◽  
Magnetic Abrasive Finishing ◽  
Abrasive Finishing ◽  
Glass Lens ◽  
The Magnetic Field

The traditional magnetic abrasive finishing (MAF) process, the magnetic flux density at the bottom of the magnetic pole is unevenly distributed, resulting in poor uniformity of the finished surface. Therefore, it is proposed to improve the surface quality by attaching a magnetic plate at the bottom of the workpiece to improve the magnetic field distribution. It is confirmed by simulation that the magnetic field distribution at the bottom of the magnetic pole is effectively improved after the magnetic plate is attached. It is proved through experiments that the magnetic plate-assisted MAF process can obtain a smoother surface. The experimental results show that the surface roughness of the glass lens improves from 246 nm Ra to 3 nm Ra through the magnetic plate-assisted MAF process within 45min.

Platform Design for Characterizing Shear Force Produced by Magnetized Magnetorheological Fluid

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.

2-D Magnetic Field Analysis of Air Cylinder with MR Sensor

2011 ◽  
Vol 121-126 ◽  
pp. 2706-2709
Author(s):  
Dan Jiang ◽  
Ping Yang ◽  
Kun Jiang
Keyword(s):  
Magnetic Field ◽  
Field Analysis ◽  
Magnetic Flux Density ◽  
Piston Motion ◽  
Element Analysis ◽  
Pneumatic Control ◽  
Magnetoresistive Sensor ◽  
Magnetic Field Analysis ◽  
Working Principle ◽  
The Magnetic Field

As a type of solid state switch, MR (magnetoresistive) sensor detects the air cylinder piston’s position in pneumatic control system. The construction and working principle of the air cylinder with MR sensor are introduced. Using 2-D magnetic field finite element analysis (FEA) method, the magnetic field distribution of air cylinder with piston motion is analyzed. Simulation results are given. The magnetic flux density characteristics are compared between piston wear or not.

A Mathematical Model of a Modified Voice Coil Energy Harvester

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.

Comparison of Affecting Factors on the Shear Stress Output of Cylinder-Typed MRF Clutch

2015 ◽  
Vol 1094 ◽  
pp. 453-457
Author(s):  
Hai Feng Ji ◽  
Chun Fu Gao ◽  
Xin Sheng He ◽  
Guang Zhang
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Affecting Factors ◽  
Bingham Model ◽  
Theoretical Derivation ◽  
Proportionality Constant ◽  
Magneto Rheological ◽  
The Relationship ◽  
The Magnetic Field ◽  
Main Influence

With the purpose of studying the main influence on the cylinder-typed magneto-rheological fluid (MRF) clutch, the relationship between the output of shear stress and its affecting factors is presented in this paper; through theoretical derivation from the Bingham Model and the cylinder-typed shear model, the stress born by the MRF in the clutch is analysed, and the affecting factors on the clutch is also simulated and verified through experiments. The study shows that as the magnetic field strengthens, the shear stress of the cylinder-typed MRF clutch grows linearly, with proportionality constant at 0.162; the increase of shear rate, relevant to the magnetic field strength, makes little difference to the torque output, with proportionality constant at 0.00026B. The results indicate that mechanical-electrical integration of clutch devices can be achieved through the control of magnetic field output of the electromagnet.

scholarly journals SHEAR STRESS MEASUREMENTS AT THE SEA BOTTOM BY MEANS OF FERROFLUIDS

2018 ◽  
pp. 88
Author(s):  
Antonino Viviano ◽  
Laura M. Stancanelli ◽  
Rosaria E. Musumeci ◽  
Enrico Foti
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Measurement Technique ◽  
Fixed Bed ◽  
Optical Readout ◽  
Experimental Campaign ◽  
Sea Bottom ◽  
Sensor Configuration ◽  
Bed Roughness ◽  
The Magnetic Field

An innovative measurement technique is proposed for investigating shear stress at sandy bottoms. This technique is based on the adoption of a ferrofluidic sensor and of an optical readout strategy. An experimental campaign is carried out for evaluating its performance. Experiments differ for the ferrofluidic sensor configuration (difference in the magnetic field) and for the bottom configurations (fixed bed or sandy bed). Calibration of the ferrofluidic sensor for the range of the investigated hydraulic condition and of the controlling magnetic field is presented. The ferrofluidic technique is promising when applied at sandy bottoms, as neither adhesion processes between sand grains and ferrofluid or influence of impacts of grains on the measurement are observed. In particular, the preliminary measure performed indicated that the ferrofluidic sensor is capable of sensing the different bed roughness.

scholarly journals The influence of conductive passive parts on the magnetic flux density produced by overhead power lines

2019 ◽  
Vol 32 (4) ◽  
pp. 555-569
Author(s):  
Slavko Vujevic ◽  
Tonci Modric
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Density ◽  
Biological Effects ◽  
Research Work ◽  
Power Lines ◽  
Magnetic Flux Density ◽  
Human Beings ◽  
Overhead Power Lines ◽  
The Magnetic Field

There has been apprehension about the possible adverse health effects resulting from exposure to power frequency magnetic field, especially in the overhead power lines vicinity. Research work on the biological effects of magnetic field has been substantial in recent decades. Various international regulations and safety guidelines, aimed at the protection of human beings, have been issued. Numerous measurements are performed and different numerical algorithms for computation of the magnetic field, based on the Biot- Savart law, are developed. In this paper, a previously developed 3D quasistatic numerical algorithm for computation of the magnetic field (i.e. magnetic flux density) produced by overhead power lines has been improved in such a way that cylindrical segments of passive conductors are also taken into account. These segments of passive conductors form the conductive passive contours, which can be natural or equivalent, and they substitute conductive passive parts of the overhead power lines and towers. Although, their influence on the magnetic flux density distribution and on the total effective values of magnetic flux density is small, it is quantified in a numerical example, based on a theoretical background that was developed and presented in this paper.

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