A Novel Measurement Method for Investigating the Lift-Off Behavior of Gas Polymer Bearings

Abstract Gas polymer bearings (GPBs) are innovative machine elements for supporting high-speed rotors in oil-free turbomachinery applications. By using air as the lubricating medium, GPBs operate without contamination from lubricating oil. This property makes GPBs eminently suitable for use as bearings in air compressors of fuel cell systems. In operating scenarios with frequent start–stop cycles, the utilization of GPBs can result in increased wear during the run-up and coast-down phases and lead to a shorter service life. The measurement of frictional torque in order to determine the rotor lift-off and touch-down speeds is of great importance for investigating the lift-off behavior. This paper presents a novel experimental method for measuring the frictional torque of GPBs. Existing test rigs feature undesirable friction in their design, which introduces measurement deviations, or stand out due to a complex design to compensate for errors such as parasitic loads, making the measurement results difficult to interpret. The new test rig addresses these problems and leads to more precise results with a reduced level of complexity. The method used to apply the static bearing load and the direct mounting of the investigated GPB on load cells represent the unique features of this study. This novel method has the potential of being established as a new standard for future investigations of lift-off behavior of GPBs and gas foil bearings (GFBs). The experimental results are compared to the results of the commonly used measurement method, in order to demonstrate the improvement.