Friction power analysis and improvement for a tilting-pad journal bearing considering air entrainment

This paper analyses the effects of air on oil-air distribution and energy characteristics of a tilting-pad journal bearing via computational fluid dynamics. With a gaseous cavitation model, air entrainment from an outlet boundary is analysed for the TPJB at a 3000 rpm rotation speed under a 180 kN load. The simulated bearing friction power is consistent with the experimental data, which indicates that the air entrainment from the outlet boundary is near the actual working conditions. According to the analyses, the shear stress of the loaded area is mainly influenced by velocity gradient in the normal direction to the rotor-side wall, whereas the shear stress of the unloaded area is mainly influenced by air volume fraction. With air cavitation and entrainment, the air volume fraction increases and affects the viscosity of a mixture considerably, thereby eventually influencing the shear stress on the rotor-side wall and bearing friction power. On the basis of this relationship, an improvement, which closes two oil inlet holes of the unloaded area whilst increasing the oil-supplied pressure of the loaded area, is proposed to remarkably decrease the bearing friction power whilst keeping load capacity. Simulation results validate the effectiveness and feasibility of the improvement.