Academic literature on the topic 'Constant speed of rotating magnetic field'
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Journal articles on the topic "Constant speed of rotating magnetic field"
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Hung, Sheng Lun, and Jik Chang Leong. "Effects of Regional Magnetic Field on Rotating MHD Flow Field of Unity Magnetic Prandtl Number." Journal of Applied Mathematics 2012 (2012): 1–17. http://dx.doi.org/10.1155/2012/804105.
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This work numerically studies the flow pattern of a magnetic fluid filled within an annulus whose inner cylinder is moving at a constant rotational speed, while the outer cylinder is stationary but under the influence of a nonuniform external magnetic field. The magnetic field consists of four basic configurations, that is, completely circular, semicircular, quarter circular, and alternately quarter circular. The strength of the external magnetic field is characterized using a reference Hartmann number. As the reference Hartmann number increases, the fluid elements need to overcome greater resistance to enter the region with magnetic field. Hence, there always exists an apparent recirculation cell within the region without externally applied magnetic field. The strength and size of the recirculation cell depend on the reference Hartmann number, the number and size of the discrete regions without external magnetic field. Only the shear stress on the moving cylinder always increases in magnitude with the reference Hartmann number and the span of the single external magnetic field region. Splitting and separating the external magnetic field may increase the magnitude of the shear stress on the moving inner cylinder but decrease that on the stationary outer cylinder. If the magnitude of the shear stress on the outer cylinder reduces beyond zero, a shear stress in the opposite sense will increase in magnitude with Hartmann number.
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Jacob, Angelo, and Nuno Monteiro. "A new concept of superelevation in magnetic levitation – prodynamic." Transportation Systems and Technology 4, no. 4 (December 19, 2018): 77–111. http://dx.doi.org/10.17816/transsyst20184477-111.
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Background: The topic of Magnetic Levitation systems, in terms of land mass transport, have created high expectations compared to aviation and also to the high speed railway industry. This new concept comes to revolutionize the terrestrial mass transport, in both the speeds and the subject of friction. Magnetic levitation solves the issue of attrition between material contact and as such may also be an opportunity to solve the question of constant physical superelevation.
Aim: Precisely that point of superelevation coupled with magnetic levitation, eliminating the rigid physical structures to laterally lift the vehicle in a curve. Current magnetic levitation systems do not address this issue of dynamic superelevation. It’s exposed an improvement technology which is a theoretical possibility of a track through a new magnetic line can apply necessary rotation to the vehicle in curve and adjust its rotation according to the speed that vehicle moves.
Methods: In order to make this system to work it is suggested the introduction of a magnetic field in the new line, which will allow the vehicle to rotate in curves and will negate the need of the conventional static superelevation.
This study appeared as a result of an investigation of a master's thesis in civil engineering at ISEP, where the participants created the concept of dynamic superelevation in the context of magnetic levitation. The project was applied to the reformulation of an existing railway network. The study base of this model resulted from a broad survey of current magnetic levitation systems. Then came the idea of creating a third dynamic magnetic field to operate the curved superelevation.
Results: The result of the study was the creation of a new "monorail" system of simple and geometrically constant structure. The new line has the advantage of providing a simple and constant geometry, facilitating the manufacture, assembly and thus making it much more economical compared to the current systems. The cross-section allows the vehicle to fit perfectly and with the creation of rotating magnetic fields, the vehicle can be turned to both sides, at the required inclination, according the speed. With this new concept called ProDynamic, the geometry design in plan is totally independent of the speed practiced by the vehicle, where it can travel in curve at different speeds, but with the same lateral no-compensated acceleration, without detriment of passenger comfort.
Conclusion: Combining existing systems with this new concept, it is possible to create a total freedom in curves and superelevation, which will provide a maximum comfort and significant construction savings. There is therefore no longer a problem of deficiency or excess cant, as currently exists on railways. The advantage in the ProDynamic system is that it is possible to greatly reduce or even eliminate the lateral no-compensated acceleration.
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Roychoudhuri, S. K., and Manidipa Banerjee (Chattopadhyay). "Magnetoelastic plane waves in rotating media in thermoelasticity of type II (G-N model)." International Journal of Mathematics and Mathematical Sciences 2004, no. 71 (2004): 3917–29. http://dx.doi.org/10.1155/s0161171204404566.
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A study is made of the propagation of time-harmonic plane waves in an infinite, conducting, thermoelastic solid permeated by a uniform primary external magnetic field when the entire medium is rotating with a uniform angular velocity. The thermoelasticity theory of type II (G-N model) (1993) is used to study the propagation of waves. A more general dispersion equation is derived to determine the effects of rotation, thermal parameters, characteristic of the medium, and the external magnetic field. If the primary magnetic field has a transverse component, it is observed that the longitudinal and transverse motions are linked together. For low frequency (χ≪1,χbeing the ratio of the wave frequency to some standard frequencyω∗), the rotation and the thermal field have no effect on the phase velocity to the first order ofχand then this corresponds to only one slow wave influenced by the electromagnetic field only. But to the second order ofχ, the phase velocity, attenuation coefficient, and the specific energy loss are affected by rotation and depend on the thermal parameterscT,cTbeing the nondimensional thermal wave speed of G-N theory, and the thermoelastic couplingεT, the electromagnetic parametersεH, and the transverse magnetic fieldRH. Also for large frequency, rotation and thermal field have no effect on the phase velocity, which is independent of primary magnetic field to the first order of (1/χ) (χ≫1), and the specific energy loss is a constant, independent of any field parameter. However, to the second order of (1/χ), rotation does exert influence on both the phase velocity and the attenuation factor, and the specific energy loss is affected by rotation and depends on the thermal parameterscTandεT, electromagnetic parameterεH, and the transverse magnetic fieldRH, whereas the specific energy loss is independent of any field parameters to the first order of (1/χ).
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Siddiqui, Abuzar Abid, and Ali J. Chamkha. "Thermo-magnetohydrodynamic effects on Cu + engine oil/water nanofluid flow in a porous media-filled annular region bounded by two rotating cylinders." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 12 (February 16, 2020): 2360–75. http://dx.doi.org/10.1177/0954406220906435.
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We examine the thermo-magnetohydrodynamic effects on nanofluid flow in a porous circular annular region bounded by two rotating cylinders in the presence of a constant radial magnetic field but variable thermal conductivity. The nanofluid consists of a sample liquid (water/ engine oil) along with suspended copper nanoparticles. This physical problem is formulated and analytical solutions for the governing equations are obtained by using the homotopy analysis method in the form of the physical variables such as, the pressure, fluid speed, temperature, shear stress, heat transfer, and the concentration of nanoparticles. The obtained results are compared with the existing results for the clear fluid and are found in excellent agreement. The effects of the field parameters on these physical variables are studied. It is found that the fluid speed (pressure) increases (decreases) with the Forchheirmer coefficient, porosity, applied magnetic field intensity, and the angular speed of the outer cylinder, but it decreases with the angular speed of the inner cylinder for both liquids. The reverse flow exists if the inner and outer cylinders are rotating in the opposite directions for both the liquids. Furthermore, the thermal transfer rate in the engine oil is lower than that in water. If the annulus region is squeezed, then the fluid speed decays while the pressure rises. The temperature and the thermal transfer rate decay if we march from the inner cylinder to the outer one. The porosity and the angular speed of the outer cylinder enhance the viscous dissipation and shear stress.
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Shih, Alexander H., and Steven Y. Liang. "Magnetic Levitation and Rotation for Feasibility of Free-Form Machining." Applied Mechanics and Materials 496-500 (January 2014): 1048–51. http://dx.doi.org/10.4028/www.scientific.net/amm.496-500.1048.
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This paper presents a new transformative manufacturing methodology for free-form machining. An experimental prototype machine is constructed to levitate and rotate an object attached with sharp edges, which act as a cutter for the purpose of performing machining processes. This device aims to lead to a technological breakthrough, overcoming the limitation of the workpiece features, and achieve greater free-form machining capability. The construction of curved holes and interior surfaces are constrained by the geometry of the machine tool. The proposed concept creates a new device that uses a magnetic field generator as a base. It is loaded with a constant power imposing a vertical physical force to balance gravity and stabilize the cutting tool. With the uniqueness of a preferred orientation between the tool and the base, a rotating surface placed below the base permits the rotation of the cutting tool in order to achieve desired tool rotation speed. A smooth and controlled cut is achieved on a soft material. The result shows the feasibility of the device to achieve similar outcomes as a machine tool.
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Selimefendigil, Fatih, and Ali J. Chamkha. "MHD mixed convection of nanofluid in a three-dimensional vented cavity with surface corrugation and inner rotating cylinder." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 4 (February 18, 2019): 1637–60. http://dx.doi.org/10.1108/hff-10-2018-0566.
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Purpose This study aims to numerically examine mixed convection of CuO-water nanofluid in a three-dimensional (3D) vented cavity with inlet and outlet ports under the influence of an inner rotating circular cylinder, homogeneous magnetic field and surface corrugation effects. In practical applications, it is possible to encounter some of the considered configurations in a vented cavity such as magnetic field, rotating cylinder and it is also possible to specially add some of the active and passive control means to control the convection inside the cavity such as adding nanoparticles, corrugating the surfaces. The complicated physics with nanofluid under the effects of magnetic field and inclusion of complex 3D geometry make it possible to use the results of this numerical investigation for the design, control and optimization of many thermal engineering systems as mentioned above. Design/methodology/approach The bottom surface is corrugated with a rectangular wave shape, and the rotating cylinder surface and cavity bottom surface were kept at constant hot temperatures while the cold fluid enters the inlet port with uniform velocity. The complicated interaction between the forced convection and buoyancy-driven convection coupled with corrugated and rotating surfaces in 3D configuration with magnetic field, which covers a wide range of thermal engineering applications, are numerically simulated with finite element method. Effects of various pertinent parameters such as Richardson number (between 0.01 and 100), Hartmann number (between 0 and 1,000), angular rotational speed of the cylinder (between −30 and 30), solid nanoparticle volume fraction (between 0 and 0.04), corrugation height (between 0 and 0.18H) and number (between 1 and 20) on the convective heat transfer performance are numerically analyzed. Findings It was observed that the magnetic field suppresses the recirculation zone obtained in the lower part of the inlet port and enhances the average heat transfer rate, which is 10.77 per cent for water and 6.86 per cent for nanofluid at the highest strength. Due to the thermal and electrical conductivity enhancement of nanofluid, there is 5 per cent discrepancy in the Nusselt number augmentation with the nanoadditive inclusion in the absence and presence of magnetic field. The average heat transfer rate of the corrugated surface enhances by about 9.5 per cent for counter-clockwise rotation at angular rotational speed of 30 rad/s as compared to motionless cylinder case. Convective heat transfer characteristics are influenced by introducing the corrugation waves. As compared to number of waves, the height of the corrugation has a slight effect on the heat transfer variation. When the number of rectangular waves increases from N = 1 to N = 20, approximately 59 per cent of the average heat transfer reduction is achieved. Originality/value In this study, mixed convection of CuO-water nanofluid in a 3D vented cavity with inlet and outlet ports is numerically examined under the influence of an inner rotating circular cylinder, homogeneous magnetic field and surface corrugation effects. To the best of authors knowledge such a study has never been performed. In practical applications, it is possible to encounter some of the considered configurations in a vented cavity such as magnetic field, rotating cylinder and it is also possible to specially add some of the active and passive control means to control the convection inside the cavity such as adding nanoparticles, corrugating the surfaces. The complicated physics with nanofluid under the effects of magnetic field and inclusion of complex 3D geometry make it possible to use the results of this numerical investigation for the design, control and optimization of many thermal engineering systems as mentioned above.
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Kuwabara, T., R. Matsumoto, and K. Shibata. "8.11. Magnetic avalanche model of mass supply in active galactic nuclei." Symposium - International Astronomical Union 184 (1998): 365–66. http://dx.doi.org/10.1017/s0074180900085247.
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We present the results of axisymmetric, two-dimentional magnetohydrodynamic (MHD) simulations of weakly ionized gas torus threaded by large scale vertical magnetic fields. The gas torus corresponds to the 100pc scale circumnuclear torus observed by HST in nearby AGNs (e.g. NGC4261) or 1010M⊙ circumnuclear gas found by CO observations in luminous IR galaxies and quasars (e.g. Scoville et al. 1991). The initial state of simulation is a constant angular momentum polytropic torus threaded by uniform vertical magnetic fields. The torus is assumed to be rotating in a static, spherical hot halo. The model parameters are Eth = vs02/(γvk02) = 5 ×10−3 and Eth = vA02/vK02 = 6.6×10−6 where γ is the adiabatic index and vs0 and va0 are the sound speed and the Alfvén speed at r = r0 respectively.
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KEAVENY, ERIC E., and MARTIN R. MAXEY. "Spiral swimming of an artificial micro-swimmer." Journal of Fluid Mechanics 598 (February 25, 2008): 293–319. http://dx.doi.org/10.1017/s0022112007009949.
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A device constructed from a filament of paramagnetic beads connected to a human red blood cell will swim when subject to an oscillating magnetic field. Bending waves propagate from the tip of the tail toward the red blood cell in a fashion analogous to flagellum beating, making the artificial swimmer a candidate for studying what has been referred to as ‘flexible oar’ micro-swimming. In this study, we demonstrate that under the influence of a rotating field the artificial swimmer will perform ‘corkscrew’-type swimming. We conduct numerical simulations of the swimmer where the paramagnetic tail is represented as a series of rigid spheres connected by flexible but inextensible links. An optimal range of parameters governing the relative strength of viscous, elastic and magnetic forces is identified for swimming speed. A parameterization of the motion is extracted and examined as a function of the driving frequency. With a continuous elastica/resistive force model, we obtain an expression for the swimming speed in the low-frequency limit. Using this expression we explore further the effects of the applied field, the ratio of the transverse field to the constant field, and the ratio of the radius of the sphere to the length of the filament tail on the resulting dynamics.
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Zhang, Jingrui, and Yanyan Li. "A Two-Dimensional Generalized Electromagnetothermoelastic Diffusion Problem for a Rotating Half-Space." Mathematical Problems in Engineering 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/964218.
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In the context of the theory of generalized thermoelastic diffusion, a two-dimensional generalized electromagnetothermoelastic problem with diffusion for a rotating half-space is investigated. The rotating half-space is placed in an external magnetic field with constant intensity and its bounding surface is subjected to a thermal shock and a chemical potential shock. The problem is formulated based on finite element method and the derived finite element equations are solved directly in time domain. The nondimensional temperature, displacement, stress, chemical potential, concentration, and induced magnetic field are obtained and illustrated graphically. The results show that all the considered variables have a nonzero value only in a bounded region and vanish identically outside this region, which fully demonstrates the nature of the finite speeds of thermoelastic wave and diffusive wave.
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Rao, Jian, Ke Wang, Boyu Wang, Qiongxuan Ge, Liming Shi, and Yaohua Li. "A special excitation system for analysis of coupling characteristics of thrust and levitation force of maglev train." Transportation Systems and Technology 4, no. 2 (September 13, 2018): 45–51. http://dx.doi.org/10.17816/transsyst20184245-51.
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Background: In the maglev train propelled by long stator linear synchronous motor (LSLSM), the thrust characteristics are one of important points to evaluate the performance of the system. However, coupling effect exists between the propulsion and levitation system. Therefore, the interference from the levitation system must be considered when the propulsion system is designed.
Aim: The article focus on the analysis of coupling characteristics of thrust and levitation force of maglev train, and a special excitation system is designed for the study.
Methods: In order to study the thrust performance under the fluctuating air gap field under laboratory conditions, a rotating synchronous motor has been designed to imitate the long stator linear synchronous motor applied in high speed maglev train. And a special excitation system is designed for the rotating synchronous motor, which can simulate the fluctuation of the exciting current during the actual operation of maglev train. The air gap of the rotating synchronous motor is kept as constant, and the fluctuating excitation current is added to the excitation winding of the rotating synchronous motor, thus the simulation of air gap magnetic field variation is achieved.
Results: The special excitation system of the experimental motor is introduced in detail.
Conclusion: The relationship between thrust and levitation force of long stator linear synchronous motor (LSLSM) in maglev train is strong coupling, non-linear, and dynamic. Complete decoupling of thrust and levitation force is not easy to be achieved. The experimental platform has been built to study the coupling characteristics of thrust and levitation force of maglev train.
Dissertations / Theses on the topic "Constant speed of rotating magnetic field"
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McKinnon, Douglas John Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Novel efficiency evaluation methods and analysis for three-phase induction machines." Awarded by:University of New South Wales. Electrical Engineering and Telecommunications, 2005. http://handle.unsw.edu.au/1959.4/21869.
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This thesis describes new methods of evaluating the efficiency of three-phase induction machines using synthetic loading. Synthetic loading causes the induction machine to draw full-load current without the need to connect a mechanical load to the machine's drive shaft. The synthetic loading methods cause the machine to periodically accelerate and decelerate, producing an alternating motor-generator action. This action causes the machine, on average over each synthetic loading cycle, to operate at rated rms current, rated rms voltage and full-load speed, thereby producing rated copper losses, iron loss and friction and windage loss. The excitation voltages are supplied from a PWM inverter with a large capacity DC bus capable of supplying rated rms voltage. The synthetic loading methods of efficiency evaluation are verified in terms of the individual losses in the machine by using a new dynamic model that accounts for iron loss and all parameter variations. The losses are compared with the steady-state loss distribution determined using very accurate induction machine parameters. The parameters were identified using a run-up-to-speed test at rated voltage and the locked rotor and synchronous speed tests conducted with a variable voltage supply. The latter tests were used to synthesise the variations in stator leakage reactance, magnetising reactance and the equivalent iron loss resistance over the induction machine's speed range. The run-up-to-speed test was used to determine the rotor resistance and leakage reactance variations over the same speed range. The test method results showed for the first time that the rotor leakage reactance varied in the same manner as the stator leakage and magnetising reactances with respect to current. When all parameter variations are taken into account there is good agreement between theoretical and measured results for the synthetic loading methods. The synthetic loading methods are applied to three-phase induction machines with both single- and double-cage rotors to assess the effect of rotor parameter variations in the method. Various excitation waveforms for each method were used and the measured and modelled efficiencies compared to conventional efficiency test results. The results verify that it is possible to accurately evaluate the efficiency of three-phase induction machines using synthetic loading.
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Wu, Wen-Juan, and 吳文娟. "New Disc Motor using Frequency of Rotating Magnetic Field Vector Independent of Rotor Speed Control." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/e82t33.
Full textBook chapters on the topic "Constant speed of rotating magnetic field"
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Kennel, Charles F. "Bursty Magnetopause Reconnection and its Consequences." In Convection and Substorms. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195085297.003.0011.
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There is at least one way in which the reconnection model of substorms is unrealistic. Rarely if ever will the interplanetary field rotate southward, stay southward, and remain constant. Even on those infrequent occasions when it does do so, steady reconnection may not be established on the dayside: We will see that dayside reconnection proceeds in bursts even then. How likely is it then that steady convection will be established on the nightside? In the next two chapters, we will fit together observations of bursty convection at the magnetopause, in the polar cap and auroral ionosphere, at various distances downtail in the plasma sheet, and beyond the average position of the neutral line in the deep tail. In this chapter, we deal with unsteady magnetopause reconnection. We start with one simple observation: The magnetopause is a source of escaping particles with energies higher than can be generated by the average convection potential across the ionosphere (Section 8.2). This, together with the fact that high-speed magnetopause flows can turn on and off between successive magnetopause crossings only minutes apart, suggests that the rate of reconnection is high for short periods of time and low for longer intervals. When the reconnection events are shorter than or comparable to MHD wave propagation times to the ionosphere, we call the reconnection “bursty.” We then let observation define the properties of bursty magnetopause reconnection. First, we discuss “flux transfer events” (FTEs), the traveling magnetic perturbations near the magnetopause (Section 8.3) that are signatures of bursty reconnection elsewhere on the magnetopause (Section 8.4). The magnitudes of the fluxes reconnected in FTEs are estimated in Section 8.5. Next, we discuss some of the ionospheric signatures of flux transfer events that might be expected on general theoretical grounds (Section 8.6). Variable dayside reconnection could be responsible for ULF magnetic activity in the polar cusp region (Section 8.7). We expect sudden magnetopause reconnection events to send Alfven waves (Section 8.8) and velocity-dispersed ions along field lines towards the polar cusp ionosphere (Section 8.9).
Conference papers on the topic "Constant speed of rotating magnetic field"
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Mohiuddin, Mohammad W., Alan B. Palazzolo, Randy P. Tucker, Desireddy V. Reddy, Andrew J. Provenza, and Albert F. Kascak. "High Temperature Magnetic Thrust Bearing: Theory and Experiment." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91544.
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Abstract Active magnetic bearings (AMBs) are being increasingly utilized in industrial applications due to their advantages over conventional bearings. They offer very low friction and wear, variable stiffness and damping, and greater tolerance of rotating mass imbalance. These unique features of AMBs have enabled design of robust rotating machinery at much higher speed with higher power concentration. The present work discusses the design of a high temperature magnetic bearing for operation at an axial thrust load of 4448N, speed 20000 rpm and temperature 538°C. Various disk profiles were considered to lower peak stresses due to centrifugal forces, including uniform (rectangular), linear tapered and hyperbolic. The predictions showed that the hyperbolic profile reduced stresses by 60% compared to the rectangular profile enabling rotor disks to operate at much higher speed. A test bearing was built with the hyperbolic disc profile. An Iron-Cobalt alloy, commercially known as Hyperco 27 was utilized for the thrust disc for its high yield strength 570MPa, high saturation flux density of 2.35T and high resistivity of 250μΩ-mm. Hyperco 50A was selected for the bearing stator, due to the lower load requirement and cost. Magnetic circuit design assumptions for the axial thrust AMB included (1) relative permeability of the magnetic material was nearly infinite, (2) fringing at gap edges as well as leakage flux were negligible, and (3) the field within the circuit was homogeneous. The initial circuit design was improved using finite element magnetic field analysis. The effective force acting on the hyperbolic rotor determined the required number of turns and current for the electromagnetic coils. Extensive structural finite element analyses suggested not to use an interference fit of the attached disk with the shaft. Rather, it was decided to utilize a sleeve and lock-nut mechanism. Inconel 718 was used for the shaft due to its slightly higher thermal expansion coefficient than Hyperco 27. The thrust AMB containment vessel included thermally-insulated radial and axial adjustment bolts to position and align the AMB inside the vessel. The AMB rotating assembly was spun using an electric motor. The magnetic force generated by the AMB at room temperature was similar to its predicted value, with a 0.85 derating factor. The magnetic force was temperature dependent and was reduced to 65% of its room temperature value, at 538°C. The maximum operating speed reached thus far in the experimental study was 5000 rpm. The magnetic bearing force was nearly invariant with rotational speed at any given temperature (e.g., room and high), while the electric current was held constant. The design indicates that the novel magnetic thrust bearing should perform well at the target operating conditions of 4448N axial load at 538°C (1000 lb-f at 1000°F), and 20,000 rpm. This has been achieved thus far only up to 5000 rpm. The force appears to be very insensitive to motion induced eddy currents up to the present maximum speed of 5000 rpm. Future work will focus on reaching the full speed target of 20,000 rpm at 538°C and 4,448 N loading.
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Doan, Minh N., Ivan H. Alayeto, Claudio Padricelli, Shinnosuke Obi, and Yoshitaka Totsuka. "Experimental and Computational Fluid Dynamic Analysis of Laboratory-Scaled Counter-Rotating Cross-Flow Turbines in Marine Environment." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83030.
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Power generation of laboratory-scaled marine hydrokinetic (MHK) cross-flow (vertical axis) turbines in counter-rotating configurations was scrutinized both experimentally and numerically. A tabletop experiment, designed around a magnetic hysteresis brake as the speed controller and a Hall-effect sensor as the speed transducer was built to measure the rotor rotational speed and the hydrodynamic torque generated by the turbine blades. A couple of counter-rotating straight-three-bladed vertical-axis turbines were linked through a transmission of spur gears and timing pulleys/belt and coupled to the electronic instrumentation via flexible shaft couplers. A total of 6 experiments in 3 configurations, with various relative distances and phase angles, were conducted in the water channel facility (3.5 m long, 0.30 m wide, and 0.15 m deep) at rotor diameter base Reynolds number of 20,000. The power curve of the counter-rotating turbines (0.068-m rotor diameter) was measured and compared with that of a single turbine of the same size. Experimental results show the tendency of power production enhancement of different counter-rotating configurations. Additionally, the two-dimensional (2D) turbine wakes and blade hydrodynamic interactions were simulated by the shear stress transport k-omega (SST k-omega) model using OpenFOAM. The computational domain included a stationary region and two rotating regions (for the case of counter-rotating turbines) set at constant angular velocities. The interface between the rotating and stationary region was modeled as separated surface boundaries sliding on each other. Velocity, pressure, turbulent kinetic energy, eddy viscosity, and specific dissipation rate field were interpolated between these boundaries.
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Arif, S. Javed, Imdadullah, and M. S. Jamil Asghar. "Rotating magnetic field based instantaneous angular speed measurement of low speed rotating machines." In 2011 International Conference on Multimedia, Signal Processing and Communication Technologies (IMPACT). IEEE, 2011. http://dx.doi.org/10.1109/mspct.2011.6150487.
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Zhang, Jin, and Fuzhu Han. "High-Speed EDM Milling Using Rotating Short Arcs Under Composite Field." In ASME 2021 16th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/msec2021-63535.
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Abstract This paper proposed a new method of high-speed electrical discharge machining (EDM) using rotating short arcs under composite field. By the Lorentz force, the electric force and the high-speed rotation of the tool electrode, rotating short arcs are generated between the tool electrode and the workpiece, which can greatly improve the material removal rate of difficult-to-cut materials such as titanium alloys and superalloys. Firstly, the machining equipment used to generate rotating short arcs was constructed. Secondly, single arc discharge experiment was carried out to investigate the motion characteristics of rotating short arcs. The result shows that the arcs can rotate between the tool electrode and workpiece under composite field. Then, the experiment of processing GH4169 was conducted to explore the machining characteristics of rotating short arcs milling, which indicated that rotating short arcs can achieve a much higher material removal rate (MRR). Additionally, it’s found that the magnetic field also has influence on debris, which is beneficial to debris removal. Finally, a comparative experiment was carried out. The MRR of rotating short arcs milling was three times than that of traditional EDM, and the tool electrode wear rate (TEWR) is only one-fifth of that of traditional EDM. The comparative experiment further verified that rotating short arcs milling can achieve higher MRR and lower TEWR.
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Spakovszky, Z. S., J. D. Paduano, R. Larsonneur, A. Traxler, and M. M. Bright. "Tip-Clearance Actuation With Magnetic Bearings for High-Speed Compressor Stall Control." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0528.
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Magnetic bearings are widely used as active suspension devices in rotating machinery, mainly for active vibration control purposes. The concept of active tip clearance control suggests a new application of magnetic bearings as servo-actuators to stabilize rotating stall in axial compressors. This paper presents a first-of-a-kind feasibility study of an active stall control experiment with a magnetic bearing servo-actuator in the NASA Glenn high-speed single-stage compressor test facility. Together with CFD and experimental data a two-dimensional, incompressible compressor stability model was used in a stochastic estimation and control analysis to determine the required magnetic bearing performance for compressor stall control. The resulting requirements introduced new challenges to the magnetic bearing actuator design. A magnetic bearing servo-actuator was designed which fulfilled the performance specifications. Control laws were then developed to stabilize the compressor shaft. In a second control loop, a constant gain controller was implemented to stabilize rotating stall. A detailed closed loop simulation at 100% corrected design speed resulted in a 2.3% reduction of stalling mass flow which is comparable to results obtained in the same compressor by Weigl et al. (1998) using unsteady air injection. The design and simulation results presented here establish the viability of magnetic bearings for stall control in aero-engine high-speed compressors. Furthermore the paper outlines a general design procedure to develop magnetic bearing servo-actuators for high-speed turbomachinery.
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Peng, Z.-C., P. Hesketh, W. Mao, A. Alexeev, and W. Lam. "A microfluidic mixer based on parallel, high-speed circular motion of individual microbeads in a rotating magnetic field." In TRANSDUCERS 2011 - 2011 16th International Solid-State Sensors, Actuators and Microsystems Conference. IEEE, 2011. http://dx.doi.org/10.1109/transducers.2011.5969457.
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Fadlallah, Hadi, Mojtaba Jarrahi, Eric Herbert, Roselyne Ferrari, Annick Mejean, and Hassan Peerhossaini. "Effects of Shear Stress on the Growth Rate of Micro-Organisms in Agitated Reactors." In ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7590.
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The effects of hydrodynamic shear stress on the growth rate of cyanobacteria Synechocystis sp. and Chlamydomonas reinhardtii microalgae cells were studied in agitated photobioreactors, since they have different motility rates and sizes. An experimental setup was designed and constructed to monitor the growth rate of the micro-organisms versus the shear rate; experiments were carried out in a well controlled environment, under constant atmospheric pressure and 20 °C temperature. Digitally controlled magnetic agitator-photobioreactors were placed inside a closed chamber with air flow for 4 weeks, under a uniform full-time light intensity provided by two 6-watt white fluorescent light sources. To study the effects of shear stress produced by mechanical agitation on the growth rate of a micro-organism, different agitation frequencies were tested. All reactors were filled with 150 ml of culture medium and micro-organism suspension, with initial dilution factors (mlsuspenion/mltotal volume) of 1/30 and 1/300 for Synechocystis and C. reinhardtii respectively. The vessels were placed on different agitating systems at the desired agitator rotation speed, and were sealed with a cotton membrane from the top in order to permit air exchange with the external environment. The micro-organisms’ growth was monitored daily by measuring the optical density of the suspensions using a spectrophotometer and was then correlated with the cellular concentration, which was measured in turn using a microscopic cell counter. Throughout the experiments pH levels and temperature were measured regularly and adjusted to 7 and 20 °C respectively in order to maintain the photosynthetic activity of the species. In addition, to measure the shear stress inside the agitated reactors, a mathematical model was derived to determine the global shear stress magnitude. To determine the local shear stress distribution, the velocity field in the reactor was measured for different agitation frequencies using PIV. Different zones of high and low shear stress were identified. The results showed that the growth rate is independent of the shear stress magnitude for Synechocystis; Synechocystis showed strong resistance, unlike C. reinhardtii, which showed linear dependence of growth rate and shear stress.
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Cuadrado, D. G., S. Lavagnoli, and G. Paniagua. "Methodology to Correct the Magnetic Field Effect on Thin Film Measurements." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42715.
Full textAbstract:
Machined ferrous metal components may carry a magnetic field, which in rotation disturb the output of electrical sensors. To minimize the effect on the electrical instrumentation, the rotating components are usually demagnetized. However, even after the demagnetization process, a residual magnetism unavoidably remains. This paper presents a methodology to predict the effects of a rotating magnetic field induced on thin-film measurements. In addition to the prediction of the magnetic effects, a procedure to correct the spurious variation in the readings of thin film gauges has been developed to enhance the fidelity of the measurements. An analytical model was developed to reproduce the bias on the electrical signal from sensors exposed to rotor airfoils with magnets. The model is based on the Biot-Savart law to generate the magnetic field, and the Faraday’s law to calculate the electromotive force induced along the measurement circuit. The model was assessed by means of controlled experiments varying the rotor tip clearance and rotational speed. The presented methodologies allowed the correction of the magnetic field effects. The raw signal of the thin film sensors, in the absence of any correction, is prone to deliver errors in the heat flux amounting to about 8% of the mean overall value. Thanks to the developed corrective approach, the residual magnetic effect contribution to the heat flux error would be 2% at most.
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Guo, Leilei, Guojun Yang, Zhengang Shi, Xingnan Liu, and Suyuan Yu. "Magnetic Field Analysis of Active Magnetic Bearings for Helium Blower of HTR-PM." In 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-15669.
Full textAbstract:
High-temperature gas-cooled reactor-pebble bed module (HTR-PM) of China, based on the technology and experience of the 10MW high-temperature gas-cooled reactor (HTR-10), is currently in the design and experiment phase. The helium blower is the key equipment in the first loop of the HTR-PM. Active magnetic bearings (AMBs) are replacing ordinary bearings as the perfect sustaining assembly for the helium blower because they have several advantages: they are free of contact, do not require lubrication, are not subject to the contamination of wear, have endurance, and control performance very well. So the AMB is the appropriate supporting assembly. The rotor’s length of the helium blower is about 3.3 m, its weight is about 4000 kg and the rotating speed is 4000 r/min. The maximal radial load of the upper AMB or the lower AMB is about 1950kg, and the maximal axial load is about 4500kg. So the axial and radial AMBs must have enough carrying capacity to support the rotor. It is difficult to design the AMB in limited space. Many factors may restrict the AMB design, for example, clearance between AMB and rotor, electric current, and environment temperature, etc. In this paper, design of magnetic field will be analyzed. Heat loss of AMB will be discussed. The designing scheme of magnetic field will offer the important theoretical base for AMB design of the helium blower of HTR-PM.
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Beermann, Laura S., Corina Höfler, and Hans-Jörg Bauer. "Design of a High-Speed Rotating Test Rig for Adaptive Seal Systems." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42329.
Full textAbstract:
Gas turbine engines are subject to increased performance and improved efficiency, which leads to rising core temperatures with additional cooling needs. Reducing the parasitic leakage in the secondary flow system is important to meet the challenging requirements. New seal designs have to be tested and optimized at engine like conditions, like high pressure of up to 9 bar and surface speed of up to 280 m/s as well as an adjusted flow field. Flexible seal designs are an innovative approach to reduce leakage mass flows significantly. Axial and radial movements during transient operating conditions can be compensated easily, thus allowing a smaller gap width and minimizing rub and heat load. This paper describes the design and construction of a new rotating test rig facility. To the knowledge of the authors, this is the only test rig with an adjustable gap width and flow field in a high pressure and speed range. The facility is capable of up to 8 bar differential pressure across the seal and up to 4 bar back pressure. The high revolution engine facilitates a surface speed of up to 280 m/s. A traversable casing allows a quick change of the gap width during operation and simulates radial and axial rotor/stator movements in the engine. The seal movement as well as the resulting gap width are measured during operation to fully understand the seal behavior. An important feature of the new test rig is the continuously adjustable pre-swirl system. It has been designed to cover the different flow conditions in the real engine. Therefore, a RANS parameter study of the pre-swirl chamber has been conducted, which shows the adjustability of different pre-swirl ratios for constant and changing inlet mass flows.