New methods for sealing, filtering and lubricating with magnetic fluids

Abstract

The use of magnetic fluids solved major problems in the development of a miniature isotope driven Stirling engine used as a power source for an artificial heart. Lubricating magnetic oil was developed for the hydrodynamic bearings in the engine. Viscosity dependence at high rates of shear, as well as other viscosity and temperature index data is discussed. A novel magnetic-type intake for the lubricantion system oil pump is presented. The intake also acts as a pre-filter. In addition, a 0.5 micron oil filter was developed and tested for long term operation with the magnetic lubricant; also wear tests were conducted on the engine's miniature high pressure gear pump operating with the oil. A rotary magnetic seal was developed to seal the magnetic oil in the crankcase. Optimization of the seal design and long-term life data are discussed. Finally, a novel linear magnetic fluid seal was developed and test data is presented. This type of seal has not been reported in the literature.