Experimental and analytical results for longitudinal electromagnetic levitation
Shampine, Rod William
Doctor of Philosophy
Electromagnetic levitation offers the possibility of working with metals in a containerless fashion. In order to realize this on a commercial basis, a solid theoretical understanding of the phenomena is needed, coupled with experimental work validating the theoretical models. In the case of the conventional conical electromagnetic levitator, models have been proposed for the forces, heating, and torque experienced by a levitated specimen. Experimental work has been primarily focused on measuring the forces. A new type of levitator is proposed in the first part of this work. The proposed levitator is suitable for use on earth as well as in micro gravity and it overcomes almost all of the drawbacks that are inherent in currently used levitation melting devices. This levitator can support samples that are an order of magnitude more massive than those that can be supported by existing devices. Further, it can levitate liquid metal samples of arbitrary shapes and provide control over the position, movement, and the rate of heat generation in them. The new levitator has the potential to become a "containerless" manufacturing process. An analysis of the currents induced in specimens supported in a longitudinal electromagnetic levitator is presented. Expressions for the forces, heating, and torque are developed. The predictions are compared with experimental measurements and are found to be in excellent agreement. Inductance, optimum specimen to coil size ratio, and effect of the number of poles are discussed in connection with the design of this class of levitator. Future directions for research with longitudinal levitators are discussed. These include finding the shape of the levitated specimen after it melts, levitation casting of significant quantities of metal, and demonstrating continuous processing of materials where only the molten portion is supported. The final part of this work fills in a significant gap in the understanding of conical electromagnetic levitators by presenting experimental results for the heating in spherical specimens, and compares these with theoretical predictions. It is found that the heating may be predicted with good accuracy, even using a simplified model.
Electronics; Electrical engineering; Mechanical engineering; Metallurgy