Variation Of Electromagnetic Force Research Articles

Effect of transverse magnetic field on magnetogasdynamic flow and heat transfer characteristics in insulated / conductive circular tubes

The regulating effect of magnetic field on magnetogasdynamic flow and heat transfer characteristics in circular tubes has important applications in many fields, but there is still a lack of relevant basic research. Considering the conductivity of the tube wall and the insufficient development of turbulence, the physical model and mathematical model of magnetogasdynamic flow in a circular tube under a given transverse magnetic field are constructed, and the numerical algorithm is designed within a theoretical framework of the finite volume method. The effect of factors including Hartman number (<i>Ha</i>) and wall conductivity ratio (<i>C</i>) on the flow and heat transfer characteristics are obtained through analyzing the distributions of velocity, turbulent kinetic energy, and temperature. Furthermore, the regulation mechanism of the transverse magnetic field is discussed by analyzing the spatial distribution of induced current, electromagnetic force and Joule heat. The results show that the distribution of velocity and the distribution of turbulent kinetic energy in the circular tube under a given transverse magnetic field are both anisotropic. The turbulent kinetic energy near the Hartmann boundary layer is much lower than that near the Roberts boundary layer, and the anisotropic distribution of velocity and turbulent kinetic energy become more and more evident with the increase of <i>Ha</i> and the extension of the flow. The transverse magnetic field has a suppression effect on the heat transfer in the tube. For different values of <i>C</i>, the average Nusselt number (<inline-formula><tex-math id="M1">\begin{document}$ \overline {Nu} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M1.png"/></alternatives></inline-formula>) shows a first-decreasing-and-then-increasing trend with <i>Ha</i> increasing, that is, there is a “saturation effect” in heat transfer suppression. When the wall conductivity is small (<i>C</i> <inline-formula><tex-math id="Z-20220808124116">\begin{document}$\leqslant $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_Z-20220808124116.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_Z-20220808124116.png"/></alternatives></inline-formula> 0.67), the change of <inline-formula><tex-math id="M2">\begin{document}$ \overline {Nu} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M2.png"/></alternatives></inline-formula> under the condition of conductive wall is basically consistent with that of an insulating wall. However, when <i>C</i> exceeds a certain value (<i>C</i> <inline-formula><tex-math id="Z-20220808124049">\begin{document}$\geqslant $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_Z-20220808124049.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_Z-20220808124049.png"/></alternatives></inline-formula> 66.67), the <inline-formula><tex-math id="M3">\begin{document}$ \overline {Nu} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M3.png"/></alternatives></inline-formula> under the condition of small <i>Ha</i> increases in comparison with that of the insulating wall, while the <inline-formula><tex-math id="M4">\begin{document}$ \overline {Nu} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M4.png"/></alternatives></inline-formula> decreases under the condition of large <i>Ha</i> . The change of flow characteristics in the circular tube results from the variation of electromagnetic force under the coupling of magnetic field and fluid, while the change of heat transfer characteristics originates from the coupling effect of the suppression of turbulence and the Joule heating. When <i>Ha</i> is small, the suppression effect of the magnetic field on turbulence is dominant, and the <inline-formula><tex-math id="M5">\begin{document}$ \overline {Nu} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M5.png"/></alternatives></inline-formula> decreases with the increase of <i>Ha</i>. When <i>Ha</i> exceeds a certain value (<i>Ha </i><inline-formula><tex-math id="Z-20220808123523">\begin{document}$\geqslant $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_Z-20220808123523.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_Z-20220808123523.png"/></alternatives></inline-formula> 222), the large accumulation of Joule heat in the circular tube enhances the heat transfer, resulting in the increase of the <inline-formula><tex-math id="M6">\begin{document}$ \overline {Nu} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220051_M6.png"/></alternatives></inline-formula> with the continuous increase of <i>Ha</i>.

Effects of structural and electromagnetic loads on vacuum vessel of Pakistan spherical Tokamak

This paper focuses on the effects of electromagnetic and structural loads on the vacuum vessel (VV) of Pakistan Spherical Tokamak (PST). The configured MAXWELL 3D and ANSYS Mechanical suits are used to investigate the different variables for structural analysis. The simulation is performed for transient current excitation of all coils and major plasma disruption, respectively. The electromagnetic (EM) loads derived from MAXWELL 3D are directly imported to the ANSYS Mechanical where structural loads are also assigned to VV. Stresses and deformations were determined from the associated loads. The 30° section of the VV with all coils is modeled in the design modeler and its step file format was imported to MAXWELL 3D. The section model was based on the axial symmetry of all coils system. By changing the thickness of inner cylinder of VV, the EM effects were studied. The variation of EM force, eddy current, and heat generation due to eddy current were studied with time for different thicknesses of the inner cylinder. As the thickness of inner cylinder decreases from 8 mm to 3 mm the magnitude of eddy current is observed to decrease uniformly for both cases (all coils and plasma disruption). The EM effect was found very strong in the case of coils transient. The results were compared using the design criterion of the RCC-Mx standard. It showed that PST geometry is safe, even 3 mm thickness of its inner cylinder can tolerate current transients of coils and associated dead loads based on the design criterion of the standard.

Electromagnetic Force Analysis of Eccentric Axial Flux Permanent Magnet Machines

Based on Schwarz–Christoffel mapping, this paper presents a fast analytical method to analyze the electromagnetic force of eccentric axial flux permanent magnet machines, considering static, dynamic, and mixed eccentricities. A quasi-3D model of an axial flux permanent magnet machine is established, and the magnetic field is obtained by Schwarz–Christoffel mapping. The electromagnetic force density is obtained by the Maxwell stress tensor method, and the electromagnetic force density is used to characterize the variation of electromagnetic force. The distribution law of electromagnetic force is investigated. The calculated results are verified by the finite element method, which has shown that the method in this paper can be widely used in the analysis of axial flux permanent magnet machines.

Physical properties of F82H for fusion blanket design

The material properties, focusing on the properties used for design analysis were re-assessed and newly investigated for various heats of reduced activation ferritic/martensitic steel, F82H. Moreover, irradiation effects on those properties were studied in this work. Most of physical properties of unirradiated F82H are insensitive to the heat-to-heat variation, and more preferable to Grade 91 specified in the ASME code. Therefore numerical analysis using data of Grade 91 can be a conservative evaluation for F82H. The change in these properties of F82H is less than 6%. Therefore the irradiation effects on thermal stress and variation of electromagnetic force in plasma disruption could be quite small in the irradiation conditions studied.

Effect of temperature on plastic deformation of sheet by electromagnetic force

Based on the new method of controlling welding distortion with trailing electromagnetic force, the electromagnetic force and the plastic deformation of sheet by electromagnetic force at different temperature was simulated by ANSYS. The circuit–electromagnetic–structural coupling was carried out with physical environment method. The results show that the magnitude of peak axial force decreases and the magnitude of peak radial force increases with increasing temperature. The variation of electromagnetic force with temperature is nonlinear. The variation rate of axial force decreases and the variation rate of radial force increases with increasing temperature. The driving force of sheet deformation decreases with increasing temperature because the axial force is larger than radial force so much. But the plastic strain of sheet by electromagnetic force increases with increasing temperature due to the decreasing yield strength. Compared with the post-welding processing, the energy supplied to processing is reduced when the electromagnetic force is applied to the controlling of welding distortion as an impactive source during welding.

An analytical method for the calculation of static characteristics of linear step motors for control rod drives in nuclear reactors

An analytical method for calculating static characteristics of linear dc step motors (LSM) is described. These multiphase passive-armature motors are now being developed for control rod drives (CRD) in large nuclear reactors. The static characteristics of such LSM is defined by the variation of electromagnetic force with armature displacement and it determines motor performance in its standing and dynamic modes of operation. The proposed analytical technique for calculating this characteristic is based on the permeance analysis method applied to phase magnetic circuits of LSM. Reluctances of various parts of phase magnetic circuit is calculated analytically by assuming probable flux paths and by taking into account complex nature of magnetic field distribution in it. For given armature positions stator and armature iron saturations are taken into account by an efficient iterative algorithm which gives fast convergence. The method is validated by comparing theoretical results with experimental ones which shows satisfactory agreement for small stator currents and weak iron saturation. >