Case Study: Knolls Atomic Power Laboratory achieves insight into CO2 foil thrust bearing wear with COMSOL Multiphysics

Knolls Atomic Power Laboratory - Customer Case Study

Knolls Atomic Power Laboratory (KAPL) was developing a 100 kWe supercritical CO2 Brayton cycle and encountered unexpected wear and even destruction of foil thrust bearings at shaft speeds below 35,000 rpm despite bearing temperatures kept well under the 400 °F limit. To investigate the failure mechanisms, KAPL used Comsol Multiphysics to run multiphysics simulations of the thrust bearing, modeling structural mechanics, fluid lubrication, heat transfer and contact interactions.

Using Comsol Multiphysics with an imported 3D geometry and a thin‑film Reynolds lubrication approach, KAPL simulated a 30 lb thrust load across 5,000–35,000 rpm and found peak film pressure of about 58.9 psi (balancing the 30 lb load), film thicknesses from ~0.12–0.28 mm, and increasing bump‑foil distortion with speed driven by viscous heating. The Comsol analysis identified thermal expansion of the bump foil due to viscous heating as a likely root cause of the wear, provided quantitative diagnostics, and directed next steps (3D cooling‑flow modeling and foil‑geometry optimization) to mitigate failures and improve bearing performance.

Knolls Atomic Power Laboratory