IMPACT OF THE DYNAMIC PERFORMANCE OF A THREE-PAD CANTILEVER BEAM GAS FOIL JOURNAL BEARING ON A HIGH SPEED TURBO-MACHINE

Gas foil bearings have gained significant interest due to the increasing demand for high-speed, high- temperature, and oil-free turbomachinery applications. Despite their increasing adoption, these bearings face challenges related to lower damping properties compared to traditional oil-lubricated coun- terparts, primarily influenced by air viscosity. However, existing research has predominantly focused on characterizing bump foil properties, resulting in scarce and occasionally contradictory data for other foil types. This study focuses on a three-pad multi-cantilever foil bearing, aiming to elucidate its structural characteristics and their impact on the rotordynamics of turbomachinery. The research integrates simulation results from a finite element (FE) computational model of a 100Krpm turbo- machine built in DyRoBeS, comparing these results with experimental measurements. The rotor's behavior is comprehensively assessed through simulations, utilizing dynamics stiffness and damping coefficients obtained from the literature. Observations indicate that a bearing pair with decreasing stiffness with rotational speed leads to a less stable rotor with higher subsynchronous amplitudes compared to a configuration with increasing stiffness. Furthermore, the synchronous response of the rotor is more pronounced in the less stable rotor-bearing configuration. To validate and refine the simulations, a series of experiments are conducted, emphasizing the correlation between the models and the actual rotor. In essence, this research contributes to the evolving understanding of gas foil bearing dynamics and the impact of high-speed turbomachinery. The study not only addresses the scarcity of data for certain foil types but also validates the computational models against real-world experiments, ensuring the applicability and reliability of the findings in practical applications.