Additively Manufactured Compliant Hybrid Gas Thrust Bearing for sCO2 Turbomachinery: Experimental Evaluation and Fluid-Structure Model Predictions

The following paper presents experimental results from rotating tests in air to 10KRPM on a new type of gas lubricated thrust bearing utilizing additive manufacturing or also known as direct metal laser melting (DMLM). The new bearing concept aims to help eliminate oil-systems in high-powered supercritical carbon dioxide (sCO₂) turbomachinery through implementing novel complex functionality into a single piece bearing design enabled by DMLM. The design involves engineering individual compliant thrust pads having hydrostatic pressurization capability to a common bearing support structure, which allows for supporting high thrust loads while absorbing misalignments found in megawatt-class rotor-bearing systems. Experimental results include measurements of film thickness, thrust load, hydrostatic flow, and pad temperatures. In addition to experimental testing, the paper advances a Reynolds equation based fluid film model coupled with a flexible support possessing compliance in 3 degrees of freedom. Results show the variation of film thickness versus rotor thrust and speed while subjecting the bearing to high levels of thrust runner run-out measured to be ~7 times the minimum film thickness. The results also show an undesired affect of load capacity decreasing with rotor speed due hydrodynamic pad tilting. Predictions of the film profile using the fluid-structure interaction (FSI) bearing model show good correlation with experimental results and also show design solutions for enhanced load capacity with higher rotor speeds.