Xdot Engineering and Analysis (United States)

Continuous Flash Sublimation (CFS) is a vapor deposition technique that shows commercially relevant deposition rates, is amenable to continuous operation, and exceeds previously reported efficiencies for the same material class.

Windage loss in small, high speed electrical machinery is often predicted using fairly simple quasi-empirical correlations. Many of the correlations used are primarily based on testing performed with larger test articles, at lower speeds, and often with liquid lubricants. This paper presents a new set of air gap windage loss test data for test articles that are more nearly representative of small, high speed electrical machinery. These data were obtained using a unique new test rig. This rig was designed around test articles that are representative of 50 to 200 kW machinery operating up to 60 krpm with air as the fluid in the rotor-stator clearance. This paper describes the new test facility and presents data for a smooth surface 72.4 mm rotor with both a smooth stator and a stator with simulated winding slots, for a range of clearances. The smooth surface results are shown to be in reasonable agreement with previously published results for annular gap windage power loss.

High speed foil bearings are currently used in increasingly demanding, high performance applications. The application under consideration is a 120 krpm natural gas turboexpander-compressor, which requires 38 mm (1.5 in.) foil journal bearings with high stiffness and load capacity to help enhance rotordynamic stability. This paper describes the development of the foil bearing for this application and includes measured stiffness and damping coefficients recorded on a high-speed dynamic bearing test rig. The dynamic test data were taken for several different foil bearing configurations with varying spring-element foil thicknesses, number of spring-element foils, and bearing shim thickness. All three parameters have a direct impact on bearing clearance. The influence of these different parameters on measured stiffness and damping coefficients and thermal performance of the bearings are presented and discussed.