Thermohydrodynamic Analysis of a Controllable Stiffness Foil Bearing with Shape Memory Alloy Springs: Experimental Tests and Theoretical Predictions

Abstract

Abstract Shape memory alloy (SMA)-gas foil bearings (SMA-GFBs) are novel gas bearings constituted of top foil, SMA springs and housing. The radial clearance, stiffness and damping coefficients of SMA-GFBs can be controlled by the bearing temperature which is determined by the electric heating of SMS springs and the cooling air. A 3D thermohydrodynamic model (THD) with the consideration of the conduction and convection of top foil, bearing housing and hollow rotor and heat energy of heated SMA springs is presented to simulate the temperature distribution of SMA-GFBs at different rotational speeds, heating powers and cooling flows. A test rig is built to measure the SMA-GFB temperature and to validate the effectiveness of the theoretical model and circumferential cooling mode. Parametric studies are conducted with different speeds, heating powers and cooling flows. Heat transfer ratios of rotor and substructure are also compared. Compared with the temperature difference of bearing temperature in the circumferential or axial direction, the influence of rotational speed and cooling flow on bearing temperature is very obvious. The phase transition process of SMA spring can be controlled by adjusting the rotor speed and the cooling flow reasonably, and then the temperature characteristics of SMA-GFB can be changed. The temperature generated by compressed gas film and heated SMA springs and cooling mode can be adjust to validate the feasibility of active changing the performance of bearing-rotor system.