Thermohydrodynamic analysis and thermal management of hybrid bump-metal mesh foil bearings: Experimental tests and theoretical predictions

Hybrid bump-metal mesh foil bearings (HB-MFBs) are novel gas foil bearings (GFBs) composed of foil strips and metal mesh blocks (MMBs) in bearing substructure. HB-MFBs provide more advantages than traditional foil bearings, such as high structural damping, assembly accuracy, and ability to work at high temperatures. A thermohydrodynamic model of HB-MFBs was proposed to predict the bearing temperature field with various bearing loads and rotational speeds. The theoretical model considered the complex thermal boundary of bearing substructure in this high-performance foil bearing, including the top foil, bump foil, and MMBs. A detailed thermal-transfer model of hollow rotor was introduced to calculate the heat energy transferring through the rotor shell to the surrounding ambient. Both thermal and centrifugal growth of hollow rotor were considered because of the thin-air film of GFBs to avoid bearing failure. A test rig used to measure the bearing temperature distribution with static load and various rotational speeds was built to validate the proposed thermohydrodynamic model. Different thermal managements with cooling air flow in hollow rotor and bearing substructure were applied to decrease the bearing temperature. The influence of load carry coefficients on bearing peak temperature was investigated with respect to rotational speed. A comparison of heat carry ratios between hollow rotor and bearing substructure was also conducted. The heat energy conducted through the bump foil region and MMB region was analyzed to validate the high-temperature capacity of HB-MFBs.