Advanced Compliant Foil Bearings and Seals for Supercritical CO2

Supercritical CO2 power cycles offer the promise of high efficiency in a compact footprint with a potential to offer disruptive changes to the US energy infrastructure. Applications include bottom cycles for electric co-generation power plants, nuclear power production, concentrated solar and other renewables as well as propulsion engines for space propulsion. Aerodynamic design theory dictates that the turbomachinery components for such power cycles will operate at high rotation speed with high-power density. Given these high operating speeds and performance requirements such as operation to 700oC, traditional off-the-shelf bearing technology is not available. MiTi’s 4th and 5th generation foil bearings are ideal candidates for integration into the necessary turbomachinery components of these power cycles. The proposed program begins with a review of the performance requirements for 1 to 100 MW power systems, followed by a parametric bearing/seal design study to establish key design parameters including both compressible and incompressible lubricant designs. Experimental testing to evaluate material/coating compatibility will be conducted with sCO2 and a preliminary Phase II test rig layout will be prepared. Through exponential advancement of the foil bearing technology in the past decade, MiTi has been able to demonstrate that foil bearings are suited for a wide range of advanced turbomachinery. For example, MiTi has successfully demonstrated the integration of foil bearings into large scale turbomachinery such as multi- Megawatt hydrogen compressors, refrigerant turbogenerators and megawatt flywheels. These successful bearing technology applications were possible due to a sound understanding of the underlying physics and tribology of the foil bearing. MiTi has developed and validated its advanced analytical tools to provide accurate performance predictions to support our designing compliant foil bearings for new applications and unproven fluid regimes. The foil bearing is a key enabling technology paramount to the success of the supercritical CO2 power cycle. MiTi has demonstrated scalability of the bearing technology from 8 mm to 150 mm diameters. Such scalability will support the development of multi-megawatt supercritical CO2 cycles that will reduce the environmental impact of large scale centralized energy production. Beyond supercritical CO2 applications, advancements in compliant foil bearings will provide industry exposure and open avenues for the technology into other parallel energy solutions such as natural gas and pipeline compressors, hydrogen fuel cells, liquid refrigerant compressors, cryogenic turbopumps, ammonia compressors and a wide array of turbogenerator systems including closed Brayton cycles for terrestrial and space power.