Analysis of Oil-Air Two-Phase Flow in Thrust Bearing Spray System of a Large-Scale Hydro-Turbine Unit

The thrust bearing, which supports axial loads in the hydroturbine unit, plays a key role in its stable operation. The sprayed thrust bearing is a recently introduced technology. It consists of a spray system with a nozzle and an oil-return device, lowering oil level to reduce the oil stirring loss of the rotating parts. In this study, a full 3D model of the sprayed thrust bearing was established for numerical simulations. The oil-air two-phase flow (OATP) method and thermo-hydrodynamic (THD) analysis method were used to investigate the sprayed lubrication conditions. By comparing the cases with and without the spray system, the characteristics of oil temperature, frictional losses, and vortex distribution within the oil tank were analyzed. The results show that the spray lubrication system can reduce the temperature of the oil film by 1.65°C and decrease bearing stirring losses by 44.1%, thus improving the unit’s operational efficiency. The OATP method provides a more accurate representation of the flow conditions within the bearing. While the spray system effectively reduces oil stirring, it also induces more chaotic flow, leading to the formation of vortices between the bearing pads. These vortices lead to energy dissipation, increasing the energy losses of the bearing. The study highlights the impact of the spray structure on the flow characteristics, temperature distribution, and energy dissipation of the thrust bearing. It is beneficial for improving the lubricating function and reliability of the bearing.