Superconducting rotating machines

The opportunities and limitations of the applications of superconductors in rotating electric machines are given. The relevant properties of superconductors and the fundamental requirements for rotating electric machines are discussed. The current state-of-the-art of superconducting machines is reviewed. Key problems, future developments and the long range potential of superconducting machines are assessed.     

Unsteady MHD rotating flow over a rotating sphere near the equator

The unsteady rotating flow of a laminar incompressible viscous electrically conducting fluid over a rotating sphere in the vicinity of the equator has been studied. The fluid and the body rotate either in the same direction or in opposite directions. The effects of surface suction and magnetic field have been included in the analysis. There is an initial steady state that is perturbed by a sudden change in the rotational velocity of the sphere, and this causes unsteadiness in the flow field. The nonlinear coupled parabolic partial differential equations governing the boundary-layer flow have been solved numerically by using an implicit finite-difference scheme. For large suction or magnetic field, analytical solutions have also been obtained. The magnitude of the radial, meridional and rotational velocity components is found to be higher when the fluid and the body rotate in opposite directions than when they rotate in the same direction. The surface shear stresses in the meridional and rotational directions change sign when the ratio of the angular velocities of the sphere and the fluid ₀. The final (new) steady state is reached rather quickly which implies that the spin-up time is small. The magnetic field and surface suction reduce the meridional shear stress, but increase the surface shear stress in the rotational direction.     

Optimized calibration and measurement procedures in rotating analyzer and rotating polarizer ellipsometry

Accurate spectroellipsometric (SE) measurements in the rotating analyzer (RAE) or rotating polarizer (RPE) configurations require accurate values of the polarizer/analyzer(/retarder) azimuths. While the readings are usually fairly accurate, true values are influenced by possible offsets between the plane of incidence, physical axes of the elements, and the instrument scales. The offsets are often determined by specialized calibration procedures. We describe SE measurements designed to obtain the calibration parameters together with the target ellipsometric spectra. We use multiple settings of the polarizer (analyzer) azimuths in RAE (RPE), respectively, to optimize precision and accuracy of SE measurements, and to economize measurement time. The optimization concerns the choice of measurement parameters as well as the subsequent data analysis. We present in detail examples of visible-ultraviolet measurements.     

Magnetic rotating disk viscometer

A rotating disk viscometer has been developed aiming at measuring the viscosity at the critical consolute point of binary mixtures in the true hydrodynamic limit. The viscometer consists of a small magnetized disk set into slow rotation by a uniformly rotating magnetic field. The liquid is continuously sheared and no frequency effects should manifest even at the critical point. The phase delay between field and disk depends on the torques acting on the disk, including that of viscous nature. The viscosity can be calculated from the knowledge of the viscous torque obtained after calibration of the viscometer using literature data for ethanol. Preliminary testing results obtained with this novel apparatus are reported.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

The elastic rotating cylinder

A fully relativistic formulation is presented for an infinitely long, elastic cylinder of constant density, rotating uniformly about its axis. The problem is reduced to a non-linear differential equation in the displacement which is linearised to obtain classical and special relativistic solutions. These are compared with a typical general relativistic numerical solution.     

旋转机械转速计算及键相脉冲处理方法

旋转机械的转速是旋转机械故障诊断中重要的参数,为了准确地获取旋转机械的转速,有效地对旋转机械进行阶次分析和计算转速谱阵,根据光电传感器采集转速信号的特点,提出了如何判断键相脉冲是否缺失,并利用线性插值方法对其修正.详细介绍了两种常见的转速计算方法,并对采集的转速键相信号进行了转速计算.经实验表明,该方法准确可行,可以准确地计算出在脉冲丢失情况下的转速,尤其是低采样率情况下,可以避免因脉冲丢失而引起的转速剧烈波动,获取准确的转速曲线.     

基于USB技术和旋转编码器的旋转运动检测与控制系统

本文介绍了USB技术 ,旋转编码器的原理 ,阐述了系统的原理和结构 ,软件和硬件的具体实现 ,达成了对直流电机旋转运动的检测与控制     

Counterflow in rotating superfluid helium

We have observed a variety of effects involving thermal counterflow in rotating superfluid helium. In particular, the temperature and chemical potential gradients associated with the motion of vortex lines have been measured. The two-fluid equations for helium in rotation have been solved for channel flow in a channel of finite height and the results are compared with our data. Interesting effects associated with the onset of turbulence and with the onset of vortex line depinning are discussed.Supported by a grant from the National Science Foundation.     

The ISSP Tokyo rotating cryostat

The rotating dilution refrigerator has been built up and tested to study topology and dynamics of vortices in thin helium films in porous glasses. The torsional oscillator method is considered as the basic technique to be used. We are able to rotate the cryostat with angular velocity up to 6.3 rad/s and resolve changes of about 0.3 mrad/s. The 40mK minimum temperature of the cryostat does not change up to the highest angular velocities.     

Cooling systems of rotating molds

In the last 20 years the method of high-speed (as a rule, higher than 10³ K/sec) metal solidification from the liquid state has found wide application in manufacture of materials. It offers the possibility to fix metastable phases, to extend the range of solid solutions, to form an amorphous state, and thereby to obtain materals whose physicomechanical properties are superior to those of traditional alloys [1]. Methods of high-speed solidification are also employed in the manufacture of either disperse particles (powders) or continuous products (strips, sheets, wires).Belorussian State Polytechnic Academy, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 4, pp. 492–507, April, 1993.     

Rayleigh's problem for rotating planes

Summary This paper is concerned with the application ofRayleigh's hypothesis to a certain class of three-dimensional flows. The problems dealt with are rotationally symmetric flows arising from a rotating plane in a rotating fluid, although in some cases the interpretation in theRayleigh sense is to steady non-symmetric flows. Results are compared with the steady solutions where these are available, and it would appear that in some cases the results are of more than qualitative value.

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Zusammenfassung Die Arbeit befaßt sich mit der Anwendung derRayleigh-schen Hypothese auf eine gewisse Klasse dreidimensionaler Strömungen. Die behandelten Strömungen sind rotationssymmetrisch und werden durch eine rotierende Ebene in einer rotierenden Flüssigkeit erzeugt. In manchen Fällen bezieht sich die Interpretation imRayleighschen Sinne auf stationäre nicht-symmetrische Strömungen. Die Ergebnisse werden, wo dies möglich ist, mit den stationären Lösungen verglichen, und es scheint, daß sie in manchen Fällen mehr als qualitativen Wert besitzen.

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With 4 Figures     

Vortical flow between rotating ellipsoids

Summary. Experimental results on incompressible viscous flows in the gap between rotating spheroids are presented. Oblate ellipsoids are discussed as a connecting link between a sphere and a disk, while a prolate ellipsoid represents the geometrical intermediate stage between a sphere and a cylinder. The axes ratios of the ellipsoids are A : B=2 : 1 and A : B=1 : 2, respectively. The basic flow field and the occurring instabilities in form of Taylor- and cross-flow vortices have been studied by flow visualization. The common properties and their differences regarding the various flow patterns of the disks, spheres, cylinders as well as of the oblate and prolate ellipsoids are treated. The location of the generation of the different vortex systems at the various rotating bodies is determined. A comparison of the friction torque for these bodies of rotation is given by diagrams. Finally, the theoretically derived curves for the friction torque of the disks, spheres and cylinders are compared with the experimentally obtained data for the oblate and prolate ellipsoids.Dedicated to Prof. Dr.-Ing. Dr. techn. E. h. J. Zierep on the occasion of his 75th birthday.     

Flow over compliant rotating disks

Flow over compliant materials and compliant coatings has been studied for decades because of the potential of using such materials for laminar-flow control. Since boundary layers in most flows of engineering interest are three-dimensional the classic rotating-disk flow geometry, the paradigm for studying three-dimensional boundary layers, has been adapted to investigate flow over compliant rotating disks. This paper reviews the literature on the existing experimental and theoretical research on flow over compliant rotating disks. The article concludes by evaluating the status of the available results and their implications as regards future research routes to investigate the capabilities of compliant materials for laminar-flow control.