Electromagnetic Brake Research Articles

Cardiopulmonary Exercise Testing in Young Asthmatic Children Ages 6-10 Years Old

� Abstract≤The aim of this study was to establish the feasibility of a minute incremental exercise testing protocol in young asthma children. Twenty-two children with clinically diagnosed mild to moderate asthma volunteered to participate. The maximum incremental exercise test was performed using a cycle ergometer with an electromagnetic braking. A warm-up unloaded for 2 minutes then the workload was started at 40 watts for 2 minutes, and then stepwise increments of 8 watts per 2 minutes were applied. The pedaling frequency was set at 50 rpm. Ventilation and gas exchange were measured with a breath-by-breath automatic metabolic measurement system. Results showed that this test was well tolerated by all asthmatic children. Most of the children reached the VO2 plateau and satisfied the criteria for maximal respiratory exchange ratio of i 1. This Study demonstrated that this testing protocol was suitable for young asthmatic children.

Relationship between F Value and Slag Entrapment in Mold with Electromagnetic Brake

An experimental device is designed to control slag entrapment of molten steel with ElectroMagnetic Brake(EMBR). Mercury was taken to simulate the liquid steel flow in the mold. The factors which affect slag entrapment with EMBR are studied, such as position of magnets, distribution of magnetic flux density and submerged depth of Nozzle. Experimental results show that the posibility of power entrapped by liquid steel was smallest as magnetic flux density B=0.3T, meanwhile, it was found that F value decreases with increasing immersion depth. Indeed, the occurrence probability of the slag entrapment decreases while d=45 mm (d is distance from the centre of SEN to the centreline of magnetic core.) instead of d=25 mm. The submerged depth within 30~50 mm are suitable to the level fluctuation in EMBR conditions in this experiment.

The use of an electromagnetic brake to improve the dynamic stability of a power system

The use of an electromagnetic brake to improve the dynamic stability of a power system is considered. Abrief review of existing methods and devices for improving dynamic stability and also a review of the use of electromagnetic brakes in industry are presented. An example of the construction of an electromagnetic brake for use in power systems is proposed. The results of an investigation of the effect of the electromagnetic brake on the dynamic stability of the simplest system are given, and technical requirements on the parameters of the electromagnetic brake are formulated.

Effect of Electromagnetic Ruler Braking (EMBr) on Transient Turbulent Flow in Continuous Slab Casting using Large Eddy Simulations

Static electromagnetic braking (EMBr) fields affect greatly the turbulent flow pattern in steel continuous casting, which leads to potential benefits such as decreasing flow instability, surface defects, and inclusion entrapment if applied correctly. To gain a fundamental understanding of how EMBr affects transient turbulent flow, the current work applies large eddy simulations (LES) to investigate the effect of three EMBr ruler brake configurations on transient turbulent flow through the bifurcated nozzle and mold of a liquid-metal GaInSn model of a typical steel slab-casting process, but with deep nozzle submergence and insulated walls with no solidifying shell. The LES calculations are performed using an in-house graphic-processing-unit-based computational-fluid-dynamics code (LES-CU-FLOW) on a mesh of ~7 million brick cells. The LES model is validated first via ultrasonic velocimetry measurements in this system. It is then applied to quantify the mean and instantaneous flow structures, Reynolds stresses, turbulent kinetic energy and its budgets, and proper orthogonal modes of four cases. Positioning the strongest part of the ruler magnetic field over the nozzle bottom suppresses turbulence in this region, thus reducing nozzle well swirl and its alternation. This process leads to strong and focused jets entering the mold cavity making large-scale and low-frequency (<0.02 Hz) flow variations in the mold with detrimental surface velocity variations. Lowering the ruler below nozzle deflects the jets upward, leading to faster surface velocities than the other cases. The double-ruler and no-EMBr cases have the most stable flow. The magnetic field generates large-scale vortical structures tending toward two-dimensional (2-D) turbulence. To avoid detrimental large-scale, low-frequency flow variations, it is recommended to avoid strong magnetic fields across the nozzle well and port regions.

THE MATHEMATICAL MODELLING OF LINER MOVEMENT IN A MAGNETIC COMPRESSOR: ELASTIC, LIQUID AND PLASTIC LINER MODELS COMPARISON

The paper is aimed to model the electromagnetic acceleration and braking of the liner in magnetic compressor. The 2D approach corresponding to the longitudinal section of spatial region is considered. Liquid, elastic, and plastic models of the liner are presented. The comparative analysis of calculation results for different models and their correlation with experimental data are carried out. The research of the influence of circuit parameters on liner braking is done.

INFLUENCE OF MAGNETIC FIELD INTENSITY MATCH OF FC MOLD II ON METAL FLOW

Electromagnetic brake(EMBr) affects the field in mold during the slab continuous casting process.Flow control moldⅡ(FC MoldⅡ) has been developed to resolve the defects of the third generation(flow control mold) of EMBr which the braking effect on meniscus is too strong to make the surface excessively stabilize and it would be prone to freezing and related defects.To gain a fundamental understanding of FC MoldⅡ,a mercury physical model was developed to investigate the influence of the magnetic field intensity match on metal in FC MoldⅡbased on the 1350 mm×230 mm slab continuous casting process in a factory.The regime and velocity distribution in mold were measured by ultrasound Doppler velocimeter(UDV) with the maximum magnetic field intensity of the upper pair of magnetic poles B_1=0.18,0.36 and 0.50 T respectively and the maximum magnetic field intensity of the down pair of magnetic poles B_2=0.50 T,while the mold casting speed is 0.41,0.52 and 0.82 m/min respectively corresponding to the practical casting speed 1.00, 1.30 and 2.00 m/min respectively.The influences of the magnetic field intensity match on the discharged from the nozzle,the near the meniscus and the washing intensity to the mold narrow wall were analyzed and studied.The results showed that,when the magnetic field intensity match of the upper and the lower pair of magnetic poles B_1/B_2≤1,with the continuous casting speed increasing, the value of B_1/B_2 should increase in order to get an ideal braking effect.The value of B_1/B_2 should be 0.36,0.72 and 1.00 respectively when the model casting speed is 0.41,0.52 and 0.82 m/min respectively.The increasing of the intensity of the magnetic field reduces the flow passage effect caused by EMBr,and is conducive to the formation of the plug under the electromagnetic braking region.

Enclosing Control Based on Prohibition by Brake Operation

Passive dynamic control (“PDC”) is a mechanical system control method based on an inherently safe design using a braking mechanism effectively. In this paper, follow-up control of pneumatic cylinders using PDC is described. Because conventional control methods using only an actuator do not have a stopping mechanism, it is difficult to prevent the controlled object from deviating from the target trajectory. On the other hand, PDC can prevent deviations of the controlled object, and return it to the target trajectory. Since this control was developed with an image of enclosing the controlled object to the target trajectory by gradually narrowing the wide area around the target trajectory, it is referred to as “enclosing control”. An experimental setup using two PDC pneumatic cylinders equipped with electromagnetic friction brakes and load cells was developed. The effectiveness of the enclosing control method is verified through experiments of follow-up control for a circular trajectory and compared with PI control. In addition, the enclosing control method is applied to follow-up control for a straight line trajectory.

Temperature Rise Optimization Design and Thermal Vacuum Experiment on Coil of Space Manipulator Electromagnetic Brake

Temperature rise optimization design of space manipulator electromagnetic brake coil is done,using a new method which combines genetic algorithm with penalty function.Firstly,optimization model of space manipulator electromagnetic brake coil is obtained with the objective of temperature rise,which considers the restrictions such as electromagnetic force,current and magnetic density.Then,a method combining penalty function with genetic algorithm is proposed to solve the nonlinearity of constraint conditions in optimization model.The method is suitable for global optimization,and guarantees that the solution is always feasible in whole calculation process.The optimization result demonstrates that temperature rise is reduced remarkably.Finally,the brake is put into thermal vacuum environment simulation equipment and temperature rise curve is drawn.The temperature rise measured in the experiment closely meets the objective obtained by the optimization calculation,and this experimental result verifies the correctness of the method and the design.

Efficiency of a DC magnetic field used for braking the flow within a continuous casting mould

AbstractThe continuous casting technology provides about 90 percent of the world steel production. The application of DC magnetic fields in form of so‐called electromagnetic brakes is considered for an effective flow control with substantial capabilities to improve the product quality or to enhance the productivity of the process. The main effect of the DC magnetic field is supposed to result in a uniform reduction of the maximum velocities in the discharging jet from the submerged entry nozzle and to damp violent turbulent fluctuations. However, the electromagnetic braking of such highly turbulent and complex flows is complicated phenomenon and has not been understood fully until now. We present numerical and experimental investigations focusing on the fluid flow in the continuous casting mould under the influence of a transverse magnetic field. Numerical calculations were performed using the software package CFX with an implemented RANS‐SST turbulence model. the non‐isotropic nature of the MHD turbulence was taken into account by specific modifications of the turbulence model. Corresponding experimental investigations were carried out at the mock‐up LIMMCAST at HZDR. The comparison between our numerical calculations and the experimental results display a very well agreement. An important outcome of this study is the feature that the magnetic field does not provide a continuous reduction of the velocity fluctuations at the nozzle port. (© 2011 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

THE BRAKING INDEX OF PSR J1734–3333 AND THE MAGNETAR POPULATION

PSR J1734−3333 is a radio pulsar rotating with a period P = 1.17 s and slowing down with a period derivative , the third largest among rotation-powered pulsars. These properties are midway between those of normal rotation-powered pulsars and magnetars, two populations of neutron stars that are notably different in their emission properties. Here we report on the measurement of the second period derivative of the rotation of PSR J1734−3333 and calculate a braking index n = 0.9 ± 0.2. This value is well below 3, the value expected for an electromagnetic braking due to a constant magnetic dipole, and indicates that this pulsar may soon have the rotational properties of a magnetar. While there are several mechanisms that could lead to such a low braking index, we discuss this observation, together with the properties exhibited by some other high- rotation-powered pulsars, and interpret it as evidence of a possible evolutionary route for magnetars through a radio-pulsar phase, supporting a unified description of the two classes of the object.

EXPERIMENTAL STUDY ON FLOWIN SLAB MOLD CONTROLLED BY JET–PATTERN MAGNETIC FIELD

A mercury model was developed to investigate the control of the jet-pattern magnetic field on the flow in medium and heavy slab continuous casting mold.The velocities in mold with and without magnetic field was measured by ultrasonic Doppler velocimeter.The influences of the magnetic field on the flow discharged from the nozzle,the flow in the mold,the flow at the meniscus and washing intensity to wall were analyzed and studied.The results showed that the flow discharged from the nozzle is suppressed,and dissipated before impinging against wall,the flow in the upper eddy is strengthened,the flow in the lower eddy is weakened,and the flow at the meniscus is improved by jet-pattern magnetic field.Compared with electromagnetic braking(EMBr) ruler,the brake effect of the the jet pattern magnetic field on the flow discharged from the nozzle and the flow at the meniscus are the better.

New DC electromagnetic wiping system for hot‐dip coating

PurposeThe purpose of this paper is to study an electromagnetic (EM) wiping process based on the EM brake (EMB) principle for hot‐dip galvanizing lines. This EMB system must act complementary to a classical air wiping system for higher drag out velocities for which the only air wiping system is no more sufficient.Design/methodology/approachAt first, the basic phenomena of the braking of a liquid driven by an upcoming strip thanks to a DC magnetic field are analyzed with a simplified analytical model. This model shows the influence of different relevant parameters such as the magnetic field intensity or the strip upcoming velocity. Then, a 2D numeric finite elements model coupling the EMs, the fluid mechanics and a deformed mesh technique is set up and shows clearly the braking effect on the liquid zinc. At last, some first results of a 3D extension of the former 2D model are shown, mainly concerning the end effects on the edge of the strip. This EM wipe effect has been experimentally demonstrated in a prototype hot‐dip galvanizing line.FindingsThe paper shows the possibility of controlling the thickness of a liquid zinc layer thanks to a DC magnetic field produced by high‐intensity permanent magnets.Originality/valueSuch an innovative way of wiping liquid zinc thanks to a DC magnetic field is able to wipe liquid zinc excess and control the liquid layer thickness with a low electric losses level. This is a major advantage compared with other known wiping techniques such as high‐frequency pin‐shaped inductors which may imply an overheating of the liquid zinc.

Fluid Flow-Related Transport Phenomena in Steel Slab Continuous Casting Strands under Electromagnetic Brake

In the current study, a three-dimensinal (3D) numerical model is built to investigate the effect of a local-type electromagnetic brake (EMBr) on the fluid flow, heat transfer, and inclusion motion in slab continuous casting strands. The results indicate that the magnetic force affects the jet characteristics, including jet angle, turbulent kinetic energy, and its dissipation rate. To reduce the top surface velocity and stabilize the top surface, the magnetic flux intensity should be larger than a critical value. With a 0.39 T magnetic flux intensity, the top surface velocity and its fluctuation can be well controlled, and less slag is entrained. The motion of argon bubbles is also studied. More bubbles, especially >2.0-mm bubbles, escape from the top surface between the mold submerged entry nozzle (SEN) and \( \frac{1}{4} \) width for the case with a 0.39 T EMBr. This may push the top slag away and create an open “eye” on the top slag. Small bubbles (≤1 mm) tend to escape from one side of wide face no matter with or without EMBr, which is induced by the swirl flow from the SEN outport. EMBr has a little effect on the overall removal fraction of inclusions; however, it affects the local distribution of inclusion in the slab. With EMBr, more inclusions accumulate the region just below the surface, thus a worse subsurface quality, whereas the inner quality of the slab is better than that without EMBr. For heat transfer in the mold, the heat flux on the narrow face and the area of possible break-out zones can be reduced by using EMBr. Prevention of bias flow and/or asymmetrical flow in mold by EMBr is also concluded.

Numerical Simulation of Flowage and Bath Surface Behavior in Continuous Casting Mold with Electromagnetic Brake

Jet shape of submerged nozzle (SEN), flowage, fluid level fluctuation and the superheat on bath surface in mold under the static electromagnetic field were 3-D simulated by using the CFX, commercial software. The results showed that electromagnetic brake (EMBR) can alter jet shape of SEN and fluid flow in the mold. And on the premise of controlling fluid level fluctuation of mold bath effectively, higher superheat of bath surface is obtained.

Effect of Static Magnetic Field on 2024 Aluminum Alloy Solidification Behavior

With the methods of macrostructure observation and temperature measurement, the paper has studied the influence rules of static magnetic field on 2024 aluminum alloy solidification structure and solidification rate. The conclusions can be concluded as follows: the static magnetic field can inhibit the growth of columnar crystals and promote the growth of equiaxed crystals; when the magnetic flux density is increased, the grain refining effect is better, the solidification rate of 2024 aluminum alloy increases remarkably, and the full solidification time is shorter; the reasons of grain refinement may be that the thermo-electromagnetic convection effect related to Peltier effect is stronger than electromagnetic braking effect, which can enhance the heat transfer and fluid flow in the solidification front, and that undercooling temperature is enlarged.

The Effects of Electromagnetic Brake on Liquid Steel Flow in Thin Slab Caster

AbstractComputational fluid dynamics (CFD) model with magneto hydro dynamics (MHD) is developed for a thin slab caster to investigate the effects of electromagnetic brake (EMBr) on liquid steel flow in continuous casting mold and to determine the EMBr practices which lead to optimal flow structure. Particle Image Velocimetry (PIV) tests in water model and meniscus flow measurements in real caster are performed to validate the predictions obtained with CFD models. The performance of different submerged entry nozzle designs, SEN 1 and SEN 2, are evaluated. The effects of nozzle submergence in relation to the applied magnetic field on mold flow structure are quantified. There are significant differences between flow structures obtained with SEN 1 and SEN 2, even though both designs have fundamental similarities and contain four ports. EMBr mainly reduces the meniscus velocities for SEN 2 as opposed to the foremost influence of EMBr for SEN 1 that is to significantly slow down the downward jet coming from the bottom ports. In addition, reducing the EMBr strength for shallow nozzle submergence and increasing the EMBr strength for deep nozzle submergence help to maintain similar meniscus activity for all conditions.

Effect of Slide Gate and EMBr on the Transport of Inclusions and Bubbles in Slab Continuous Casting Strands

AbstractThis study is to investigate the effect of electromagnetic brake (EMBr) on fluid flow and particle motion in steel slab continuous casting strands. The effect of slide gate moving on fluid flow pattern was discussed. A strong swirl and asymmetrical flow at the outports and, subsequently, inside the slab mold, was induced by slide gate. The application of EMBr would be a remedy to the swirl flow in the casting mold. Flow pattern has great influence on the trajectories of injected bubbles and nonmetallic inclusions. More bubbles tend to release from the top surface near the wide face opposite to the gate opening side without EMBr; while, they escape at the center place of the slab thickness when the EMBr was applied. Local brake type EMBr has a little effect on the overall removal fraction of nonmetallic inclusions, especially for the small ones. However, EMBr affects the distribution of inclusions on the cross section of the slab, and more inclusions were observed in the sub‐surface layer of the slab.

A Numerical Method of Macrosegregation Using a Dendritic Solidification Model, and Its Applications to Directional Solidification via the Use of Magnetic Fields

A numerical method for analyzing solidification phenomena of multicomponent alloys is presented. This method consists of macroscopic transport governing equations expressed in terms of a nonlinear multicomponent alloy model, which is coupled with the microscopic dendritic solidification model to estimate permeability. Numerical simulations were performed for channel segregation in a steel ingot and for freckles in a Ni-base IN718 remelted ingot and in Ni-10 wt pct Al directionally solidified (DS) ingots. The results show good agreement with experimental observations. The electromagnetic (EM) braking effect by static magnetic field was incorporated into the numerical method, and the anisotropic behavior of magnetic field was investigated on the DS Ni-10 wt pct Al ingots. Application of relatively low magnetic fields in the transverse to the growth direction (Bx or By) resulted in formation of distorted freckles as a result of the nonuniform liquid flow induced in the transverse direction. It is shown that a considerably high magnetic field is required to suppress the distorted freckles and other freckles developed in longitudinal direction. However, there is a risk of the breakdown of DS. On the other hand, when applying the magnetic fields parallel to the growth direction (Bz), the number of freckles inversely increased at low magnetic fields, but the freckles were eliminated by about the same level of high magnetic field as that of Bx or By. Because the parallel magnetic field suppresses the liquid flow vector components uniformly within the transverse plane, the nonuniform flow does not occur in the transverse directions. As a result, it suppresses the flow in the growth direction. It is envisioned that the application of the parallel magnetic field is beneficial in the commercial production of DS castings.

Numerical Simulation of Fluid Flow and Thermal Characteristics of Thin Slab in the Funnel-Type Molds of Two Casters

A mathematical model of three-dimensional fluid flow, heat transfer and solidification in thin slab casting is developed based on the enthalpy-porosity approach in a single-phase framework and used to analyze and compare the fluid flow and thermal behaviors in the funnel-type molds of Compact Strip Production (CSP®) and Flexible Thin Slab Casting (FTSC®) caster. An Electromagnetic Brake (EMBR) model is also incorporated into this coupled model to see the effects of EMBR on fluid flow and solidification in a CSP caster with EMBR system. The numerical treatments specific to the complex funnel-shaped mold boundaries are discussed. The obtained numerical results are partly validated by those available in literature and theoretical analyses. The fluid flow and thermal features of thin slab in CSP mold and FTSC mold are analyzed and their comparisons between them are made. It is found that the flow pattern, level fluctuation, superheat dissipation, temperature distribution and shell growth in both molds present different features. The structure of SEN strongly affects the flow pattern of the impinging jet from SEN ports, and then the dissipation mode of the melt superheat and the uniform growth of solidification shell. A four-port SEN® with two small upper ports in FTSC mold is helpful to activate the meniscus flow and increase the meniscus temperature, but high level fluctuation may occur. The EMBR in a CSP mold can both suppress the meniscus flow and increase the meniscus temperature. A complete flow-control system including the design of SEN, EMBR and operational conditions is essential for thin slab production considering their individual flow and thermal features in the funnel-type molds of CSP and FTSC casters.

Analysis of the Dynamic Behavior of a Linear Induction Type Catapult

The electromagnetic launcher, widely studied as electromagnetic gun, may also be used as a catapult for electromagnetic acceleration of aircrafts to replace steam catapult. These launchers can be realized utilizing a synchronous or asynchronous type of linear accelerator. In this paper, the second realization, which is the use of an asynchronous type of linear accelerator, is considered. Thus, a system consisting of a fixed part, realized with several sections and a moving part that brings the sled supporting the object to launch, is proposed. Each section contains a three-phase winding fed by different frequencies. The goal of this paper is to investigate moving part braking strategies once the mass has been launched. It is proposed that a method of electromagnetic braking can possibly allow the recovery of the kinetic energy.