Heshmat, H. and Dill, J. “Fundamental Issues in Cryogenic Hydrodynamic Lubrication,” Proceedings of AFOSR/ML Fundamentals of Tribology Work Shop, February 1987.
High-speed cryogenic turbomachines are required for advanced space applications. Shaft sizes are in the range of 20 to 30 mm and rotating speeds are approximately 100,000 to 150,000 rpm. The process fluid (hydrogen and oxygen) is a poor lubricant, but separate lubricant systems are precluded by the complexities introduced. Therefore, the process fluid is used as the bearing lubricant. Rolling-element bearings have a poor performance history due to wear and poor lubrication. Also, DN values are beyond the present state of the art for rolling-element bearings. However, in a cryogenic process fluid environment, fluid-film-lubricated bearings require significant attention, understanding, and knowledge of how the fluid behaves under hydrodynamic actions.
There is a considerable amount of noteworthy activity currently going on in the field of hydrodynamics. However, there are several areas where increased knowledge would substantially improve our theoretical understanding, thus allowing the successful application of theory to practical situations.