Showing papers on "Shields published in 1987"

A comprehensive study of the induced current, the electromagnetic force field, and the velocity field in a complex electromagnetically driven flow system

Abstract: A mathematical formulation is developed to describe the electromagnetic parameters and the velocity fields in an inductively stirred melt, both in the presence and the absence of shields. The theoretically predicted results are compred with experimental measurements pertaining to the induced current, the components of the magnetic flux, and the phase angle between the current and the magnetic flux. In addition, the melt velocity was also determined, using a Vives probe. The excellent agreement obtained between measurements and predictions regarding both the individual input parameters and secondary quantities, such as the electromagnetic force field and the velocity field, shows a full validation of the technique employed. It has also been demonstrated that the use of magnetic shields may be a useful way of modifying the flow patterns in these systems.

Development and test of the Shuttle/Centaur cryogenic tankage thermal protection system

Abstract: The Thermal Protection System (TPS) for the Shuttle/Centaur had to provide fail-safe thermal protection during prelaunch, launch ascent, and on-orbit operations as well as during potential abort where the Shuttle and Centaur would return to earth. The TPS selected used a helium-purged polyimide foam beneath three radiation shields for the liquid hydrogen (LH2) tank and radiation shields only for the liquid oxygen (LO2) tank (three shields on the tank sidewall and four on the aft bulkhead). An evacuated common intermediate bulkhead separated the two tanks. The LH2 tank had one 1.9-cm thick layer of foam on the forward bulkhead and two layers on the larger area side-wall. Full scale tests of the flight vehicle in a simulated Shuttle cargo bay, that was purged with gaseous nitrogen, gave total prelaunch heating rates of 25.9 kW and 12.9 kW for LH2 and LO2 tanks, respectively. Calorimeter tests on a representative LH2 tank sidewall TPS sample indicated that the measured unit heating rate would rapidly decrease from the prelaunch rate of 300 W/sq m to a desired rate of less than 4 W/sq m once on-orbit.

Magnetically shielding unit for stationary electric apparatus

Abstract: PURPOSE:To obtain a magnetically shielding unit for a stationary electric apparatus having excellent magnetically shielding effect inexpensively by forming the width of a thin magnetic plate narrow at both longitudinal ends and wide at the center. CONSTITUTION:Thin plates 7a of silicon steel to be laminated with magnetic shields 7 are formed in width narrow at both ends and wide at the center. Oblique portions are formed at the boundaries between the both ends and the center. The shields 7 are so mounted that the projecting surface of the center is disposed at a winding side on the inner surface of an outer box 2. Since the shields 7 are sufficiently thick even if a leakage magnetic flux F impregnating to the shields 4 attached to the box 2 from a winding 3 of a transformer to the like becomes maximum at the center in the elevational direction, the magnetic flux density is not saturated nor the shields 4 are abnormally vibrated. Further, since the both ends of the shields 7 having small leakage magnetic flux F are thin, the shields can be inexpensively manufactured. In addition, since the thin plates 7a of the shields 7 are laminated in the same direction as the leakage magnetic flux advancing direction, an eddy current loss in the silicon steel plates can be decreased.

Magnetic shield for stationary induction electric apparatus

Abstract: PURPOSE:To reduce the loss generating on the tank wall of the terminal of a magnetic shield, a tank cover and the bottom plate of the tank as well as to prevent a local overheating by a method wherein the magnetic shielding plate laminated in parallel with the tank wall is bent along the bent part of the tank at the center part of a phase. CONSTITUTION:Magnetic shields 6a, 6b, 6c and 7 are constituted in such a manner that the laminated layers of the magnetic shields are directed in parallel with the linear part 4a of a tank, the inclined part 4b of the tank and the bottom plate part 4c of a tank, the inclined part 4b of the tank and the bottom plate part 4c of the tank in order to reduce the loss generating on the magnetic shields. On the section in the vicinity of the center part of a phase, the magnetic shield 6a in longitudinal direction, where magnetic flux is susceptible to pass, is bent along the bent part of the tank and extended in height direction to the end section of the inclined part 4b of the tank in order to come nearer as much as possible to the state wherein the leakage magnetic flux is intruded into the tank wall. Also, on the section in the vicinity of the interphase part, the magnetic shields 6b and 6c in lateral direction, where the magnetic flux is susceptible to pass in the longitudinal direction of the tank, are arranged respectively and a magnetic shield 7 having the same lamination direction as the above-mentioned magnetic shields is arranged covering the three phases on the tank bottom plate 4c. As the magnetic flux which runs in the magnetic shields 6a is fed back to the winding without moving to the inclined part 4b, the local overheating at the inclined part 4b of the tank can be prevented.