PERFORMANCE CHARACTERISTICS OF GAS-EXPANDED LUBRICANTS IN HYBRID BEARINGS USING COMPUTATIONAL FLUID DYNAMICS
Gas-expanded lubricants (GELs) have been proposed as tunable fluids with properties that can be controlled in real-time to maximize bearing and rotordynamic performance. These binary mixtures of synthetic oil and dissolved carbon dioxide provide direct control over the lubricant viscosity by adjusting the composition of the mixture via pressure and flow control. Early work on this topic focused on the experimental measurement of GEL properties followed by analytical studies of their potential effects on bearing performance and rotordynamic stability. However, in the analytical work performed to date a single-phase lubricant mixture was assumed along with a fully pressurized bearing cavity to maintain that phase behavior. While the previously performed experimental work justified the assumptions made with that methodology, that approach was limited in its ability to evaluate more detailed fluid behavior and the potential for multi-phase behavior, as well as the implications of this for bearing performance. The goal of this study is to therefore use computational fluid dynamics (CFD) to allow for a more detailed study of the fluid behavior under a range of lubrication conditions in a hybrid bearing environment.