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.

This study conducted the experimental investigation of aerodynamic heating of Micro-scale Rotational Shearing Flow with Axial Limited-Length (MRSFALL). The temperature rise of the stator is captured by the high response thermocouples. The eccentricity ratio and clearance height are guaranteed by means of instantaneous trajectory and torsion monitoring of the rotator. The result shows that the maximum temperature rise takes place upstream of the minimum clearance height along circumferential direction. The distribution of temperature rise presents asymmetric curve along axial direction, and peak value occurs near the dimensionless axial position of −0.18. The effect of aerodynamic heating becomes notable as the rotational speed is larger than 3 × 10⁴ r/min. The effect of end leakage and the viscous dissipation have great impact on temperature rise of MRSFALL. More specially, the peak value of temperature rise at dimensionless clearance height of 0.0080 is larger than the case at dimensionless clearance height of 0.0044. Furthermore, when the eccentricity ratio is too large, the viscous dissipation is induced, and the additional temperature rise is achieved. The heat flux identification of shear flow has been realized by Sequential Function Specification Method (SFSM) and its estimation of thermal load has been given. The heat flux induced by the aerodynamic heating in this study varies from 950 W/m² to 1330 W/m².

More and more researchers have paid attention to Taylor-Couette flow whose axial dimension is much larger than other dimensions. However, featured by the limited axial length of the bearing, its flow field and convective heat transfer between the rotator and the stator are highly conglutinated with the leakage at the end of the clearance. An investigation was conducted on the flow field and convective heat transfer of small-scale Taylor-Couette flow induced by end leakage through means of numerical simulation and experimental measurement. The static pressure and temperature of the stator were captured by a micromanometer and a time-resolved infrared camera, respectively. Large Eddy Simulation (LES) was performed to reveal the instantaneous and mean flow field of the shearing flow. Results show that the flow field and convective heat transfer are tightly associated with the presence of end leakage. As approaching the end of the clearance, the flow is dominated by the axial flow induced by the end leakage, and then a series of Taylor vortices gradually distorts and tilts as moving downstream. Along the angular direction, the maximum and minimum static pressures take place near minimum clearance height, respectively. The static pressure along the angular direction and the axial velocity near the minimum clearance height as well as the Nusselt number increase with increases of the rotational Reynolds number and the eccentricity ratio while decreasing with an increase of the dimensionless clearance height. Both natural convection by buoyancy and forced convection by the shearing flow play a significant role in convective heat transfer. Compared with classic Taylor-Couette flow, the occurrence of leakage decreases the maximum static pressure while increasing the minimum static pressure. The formation and evolution of the Taylor vortex are dominated by the axial flow.