Numerical investigation in characteristics of multi-layer thrust gas foil bearing based on fluid–structure coupling field

Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization, and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive deformation characteristics. This study explores the interaction mechanism between micro-scale variable-sectional shearing flow with hyper-rotation speeds and a three-layer elastic foil assembly through bidirectional aero-elastic coupling in a Multi-layer Thrust Gas Foil Bearing (MTGFB). The bearing capacity of the MTGFB varies non-linearly with the decrease of gas film clearance, while the collaborative deformation of the three-layer elastic foil assembly can deal with different load conditions. As the load capacity increases, the enhanced dynamic pressure effect causes the top foil to evolve from a single arch to multiple arches. The hydrodynamic effects in the gas film evolve to form multiple segmented wedges with different pitch ratios, while the peak pressure of the gas film always occurs near the vaults of the top foil. As the rotational speed frequency approaches the natural frequency, the resonance of the gas film and elastic foil assembly system occurs, and a phase delay occurs between the pressure pulsation and the vibration of foils. The load capacity of the MTGFB also depends on the elastic moduli of the elastic foil assembly. Increasing the elastic modulus decreases the deformation amplitude of the top foil, whereas it increases those of the backboard and middle foil, increasing the load capacity.