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At least 433 records · Page 24

BAAM Additive Manufacturing of Magnetically Levitated Wind Turbine

ORNL worked with Hover Energy LLC (Hover) on the design of Big Area Additive Manufacturing (BAAM) extrusion components. The objective of this technical collaboration was to identify and evaluate fabrication of components using alternative additive manufacturing techniques. Multiple candidate parts were identified. A design modification to fabricate diverters using additive manufacturing (AM) was performed and the part was analyzed based on anticipated wind loading. Scaled versions of two parts were printed using the BAAM for wind tunnel testing.

17 WIND ENERGY↗

Acoustical levitation for space processing

It is pointed out that many space-manufacturing processes will require the manipulation of weightless molten material within a container in such a way that the material does not touch the container wall. A description is given of an acoustical method which can be used for the positioning and shaping of any molten material including nonconductors such as glasses. The new approach makes use of an acoustical standing wave which is excited within an enclosure or resonator.

Wang, T. G.↗

Levitation of objects using acoustic energy

Activated sound source establishes standing-wave pattern in gap between source and acoustic reflector. Solid or liquid material introduced in region will move to one of the low pressure areas produced at antinodes and remain suspended as long as acoustic signal is present.

Whymark, R. R.↗

Design analysis of levitation facility for space processing applications

Containerless processing facilities for the space laboratory and space shuttle are defined. Materials process examples representative of the most severe requirements for the facility in terms of electrical power, radio frequency equipment, and the use of an auxiliary electron beam heater were used to discuss matters having the greatest effect upon the space shuttle pallet payload interfaces and envelopes. Improved weight, volume, and efficiency estimates for the RF generating equipment were derived. Results are particularly significant because of the reduced requirements for heat rejection from electrical equipment, one of the principal envelope problems for shuttle pallet payloads. It is shown that although experiments on containerless melting of high temperature refractory materials make it desirable to consider the highest peak powers which can be made available on the pallet, total energy requirements are kept relatively low by the very fast processing times typical of containerless experiments and allows consideration of heat rejection capabilities lower than peak power demand if energy storage in system heat capacitances is considered. Batteries are considered to avoid a requirement for fuel cells capable of furnishing this brief peak power demand.

Frost, R. T.↗

The measurement of heats of solution of high melting metallic systems in an electromagnetic levitation field

A method was tested for measuring the enthalpies of mixing of liquid metallic alloying systems, involving the combination of two samples in the electromagnetic field of an induction coil. The heat of solution is calculated from the pyrometrically measured temperature effect, the heat capacity of the alloy, and the heat content of the added sample. The usefulness of the method was tested experimentally with iron-copper and niobium-silicon systems. This method should be especially applicable to high-melting alloys, for which conventional measurements have failed.

Frohberg, M. G.↗

Classifying Particles By Acoustic Levitation

Separation technique well suited to material processing. Apparatus with rectangular-cross-section chamber used to measure equilibrium positions of low-density spheres in gravitational field. Vertical acoustic forces generated by two opposing compression drivers exciting fundamental plane-wave mode at 1.2 kHz. Additional horizontal drivers centered samples along vertical axis. Applications in fusion-target separation, biological separation, and manufacturing processes in liquid or gas media.

Barmatz, Martin B.↗

Interstitial Collimating Holes for Gas-Levitation Microfurnace

Spaces between small rods direct gas flow. Wires for thin rods clamped in square array in precise square gooove. Spaces between wires are long, thin, parallel channels that direct flow of gas. Technique extended to such hard-to-machine refractory metals as tungsten and molybdenum.

Dunn, E. G.↗

Sample levitation and melt in microgravity

A system is described for maintaining a sample material in a molten state and away from the walls of a container in a microgravity environment, as in a space vehicle. A plurality of sources of electromagnetic radiation, such as of an infrared wavelength, are spaced about the object, with the total net electromagnetic radiation applied to the object being sufficient to maintain it in a molten state, and with the vector sum of the applied radiation being in a direction to maintain the sample close to a predetermined location away from the walls of a container surrounding the sample. For a processing system in a space vehicle that orbits the Earth, the net radiation vector is opposite the velocity of the orbiting vehicle.

Moynihan, Philip I.↗

An optical multipass radiation system (OMRS) for heating levitated samples

The present system for spaceborne containerless material sample heating uses lamp systems with heating efficiencies of the order of 65 percent, potentially producing 30 W/sq mm over areas of 0.3 sq cm. The effectiveness of these lamp systems has its basis in the 'multipassing' of the lamp beams to recycle fluxes not absorbed by the sample during the initial pass. The actual multipass system's performance will have a power-law dependence on the quality of the coatings and optical surfaces illuminated; a detailed study of the spectral and dichroic characteristics, surface-scattering, and optical figure specifications of the system must be completed for full characterization.

Morrow, W. H.↗

Acoustic response of a rectangular levitator with orifices

The acoustic response of a rectangular cavity to speaker-generated excitation through waveguides terminating at orifices in the cavity walls is analyzed. To find the effects of orifices, acoustic pressure is expressed by eigenfunctions satisfying Neumann boundary conditions as well as by those satisfying Dirichlet ones. Some of the excess unknowns can be eliminated by point constraints set over the boundary, by appeal to Lagrange undetermined multipliers. The resulting transfer matrix must be further reduced by partial condensation to the order of a matrix describing unmixed boundary conditions. If the cavity is subjected to an axial temperature dependence, the transfer matrix is determined numerically.

El-Raheb, Michael↗

Dynamics and control of high precision magnetically levitated vibration isolation systems

Vibration control of flexible structures has received a great deal of interest in recent years. Several authors have investigated this topic in the areas of robot manipulators, space structures, and flexible rotors. Key issues associated with the dynamics and control of vibration isolation systems are addressed. Among other important issues to consider in the control of such systems, the location and number of actuators and sensors are essential to effectively control and suppress vibration. We first address the selection of proper actuator and sensor locations leading to a controllable and observable system. The Rayleigh-Ritz modal analysis method is used to develop a lumped-parameter model of a flexible vibration isolation table top. This model is then used to investigate the system's controllability and observability including the coupling effects introduced by the magnetic bearing. This analysis results in necessary and sufficient conditions for proper selection of actuator and sensor locations. These locations are also important for both controller system's complexity and stability of point of views. A favorable pole-zero plot of the open loop transfer functions is presented. Necessary and sufficient conditions for reducing the controller complexity are derived. The results are illustrated by examples using approximate mode shape functions.

Youcef-Toumi, K.↗