An Advanced Gas Foil Bearing Using Supercritical Carbon Dioxide as the Working Fluid

As new commercial applications arise for supercritical CO2 sCO2) power generation, and higher efficiencies are achieved through higher turbine inlet pressures and temperatures, the need to improve component technologies becomes essential. Traditionally lubricated and cooled oil bearings cannot tolerate the higher temperatures, and the higher pressures makes keeping the oil separate from the working fluid an increasingly difficult challenge. These conditions strongly promote the use of the sCO2 working fluid itself as the lubricant, rather than oil.This grant application seeks to develop a new gas foil bearing that meets these advanced needs by using the sCO2 as the lubricating fluid. The proposed concept combines the best features of current foil bearing technology with new-concept design enhancements that will sufficiently advance the art by providing increased load capacity, damping, and wear resistance, as well as tolerance to the service conditions of vibration, temperature, and misalignment. To achieve project objectives, MSI will combine best-in-class technologies in pressurized hydrostatic gas bearings and hydrodynamic gas foil bearings to produce an advanced hydrostatically-assisted hydrodynamic gas bearing design, using as a starting point MSIs existing foil bearing product line. In Phase I, MSI will update its analytical models and codes to include the fluid properties of sCO2. Novel bump foil geometries and patterns will be evaluated to maximize load carrying capacity and damping characteristics. Test rigs at MSI will be used to evaluate candidate coatings for optimum start-stop wear resistance. The resulting component designs will be combined into a total assembly for first-order validation testing using air, in MSI existing facilities) evaluating hydrostatic and bumper shock resistance strategies. MSIs proposed effort directly supports both commercial and federal interests. Foil bearings are an enabling technology which allows the creation of machines that otherwise could not be built, particularly in high speed machines or in ultra-pure systems like sCO2 where contaminants, such as oil or grease, cannot be tolerated. Advancements in the technology can be immediately utilized in a variety of applications ranging from sCO2 systems, ground-based gas turbine-powered electric power generators, compressors, refrigeration equipment, vehicular systems turbochargers, fuel cell blowers), aerospace environmental control systems, auxiliary power units, small to medium propulsion gas turbines, and rocket turbopumps.