Additively Manufactured Compliant Hybrid Gas Thrust Bearing for sCO2 Turbomachinery: Design and Proof of Concept Testing

The following paper advances a new type of gas lubricated thrust bearing that utilizes additive manufacturing or also known as direct metal laser melting (DMLM) to fabricate the bearing. The motivation for the new bearing concept is drawn from the need for highly-efficient supercritical carbon dioxide (sCO₂) turbomachinery enabled through the elimination of conventional oil-lubricated bearing systems. Utilizing the process fluid of the turbomachine to lubricate the bearing system results in lowered bearing power loss, simplified mechanical design, and also enables novel oil-free hermetic drivetrains yielding a efficient emission-free machine architecture. To support the thrust loads and operating conditions indicative of high-powered megawatt-class sCO₂ turbomachinery, the bearing concept possesses complex functionality in a single piece design through combining external hydrostatic pressurization with individual flexibly mounted thrust pads. The external pressurization allows for higher load capacity while the pad flexibility allows for compliance to thrust runner static and dynamic misalignment. The paper provides a literature review of existing gas lubricated bearing concepts and follows with discussion on the bearing concept and additive design process. The paper also provides proof of concept testing results in air up to 10KRPM while supporting high loads under extreme thrust runner run-out magnitudes that were measured to be ~7times the experimental minimum film thickness values.