Oil distribution inside the under-race lubricated bearing is crucial for lubrication and cooling of high-speed ball bearings. An under-race lubricated ball bearing is modeled to numerically investigate the effects of operating parameters and feed hole configuration on the distribution behavior of lubricant oil. The results of the numerical simulation indicate that the average oil volume fraction changes with a convex trend as the outer race rotating speed increases, while it changes monotonically with the inner race rotating speed, oil volume flow rate, and oil temperature. The extent of oil spreading on the outer race, cage, ball, and inner race decreases successively. Optimizing the feed hole configuration according to the average oil volume fraction is helpful to achieve precise lubrication of the under-race lubricated ball bearing.

Investigations on the influence of different cavity structures on the reliability and cooling of thrust bearings were performed. Four cavity structure models were built. The variation laws of reliability and cooling characteristics of thrust bearing fluid domain under different structure and operating condition parameters were discussed. The influence mechanism was revealed. Four cavity structures were optimized for parameters. The results show that the high-pressure regions of the step and taper cavity structures are slender. Thrust bearings with step or taper cavity structure have better reliability and cooling. Thrust bearings with step-pocket or taper-pocket cavity structure can provide greater stiffness and damping, which effectively suppress the axial vibration of the rotor system. The depth of the cavity has the greatest effect on the load-bearing capacity of thrust bearings with different cavity structures. Through parameter optimization, the load-carrying capacities of four thrust bearings are increased by 19.23%, 37.44%, 30.60%, and 73.28%, respectively. The aforementioned investigations can offer theoretical guidance for the design and optimization of thrust bearings.

A deep understanding of oil behavior inside roller bearings is important for the precise design of bearing configurations and oil systems in aircraft engines. The numerical method is employed to track oil distribution inside cylindrical roller bearings with under-race lubrication along the circumference and radial direction, respectively. The results demonstrate that oil distribution along the circumference is periodic with the number of under-race nozzles, and higher rotating speed and lower flow rate would reduce the fluctuation amplitude. It is difficult for oil to flow through the gap between the cage pocket and rollers, and higher oil viscosity would worsen it further. In some extreme cases, the oil volume fraction near the outer race may be lower than 0.7%, causing the risk of lubricating and cooling failure. Thus, more attention should be paid to the outer race of the roller bearing with under-race lubrication, especially during the starting stage of the engine and in cold weather.

The distribution of oil and gas phases around ball–raceway local regions is an important basis and foundation for determining whether a bearing is sufficiently lubricated. To obtain the oil phase distribution law in the inner raceway–ball contact local region (IBCR) and outer raceway–ball contact local region (OBCR) of the ball bearing with under-race lubrication, the numerical simulation method is used. The effects of bearing rotation speed, oil flow rate, oil viscosity, and oil density on these two regions are studied. The results indicate that the oil phase exhibited significant periodic changes in both time and space. Compared with that in the IBCR, the oil phase distribution in the OBCR is more uniform. Increasing the bearing rotation speed and reducing the oil flow rate made the IBCR and OBCR more uniform. Changing the oil viscosity only alters the distribution pattern of the OBCR. The oil density may not affect the fluid flow state or the oil phase distribution in the bearing.

The objective of this research is to determine the influence of dual-orifice jet nozzles on the oil–air flow dynamics and oil capture performance in the under-race lubrication for high-speed bearings and to identify the optimal design parameter combinations for optimizing the oil capture performance. An experimental setup for under-race lubrication is specifically designed, complemented by a multiphase computational fluid dynamics model to elucidate the oil–air flow behavior. The response surface methodology is combined with a multi-objective particle swarm optimization algorithm to perform multi-objective optimization of the oil capture performance. The findings indicate that oil capture efficiency initially rises to a peak and subsequently declines with increasing orifice spacing, identifying an optimal orifice spacing that maximizes efficiency. While the oil flow rate from dual-orifice jet nozzles is lower than twice that of single-orifice jet nozzles, appropriate parameter matching allowed for an increase in both captured lubricant oil and efficiency. Optimized configurations achieved substantial enhancements in oil capture efficiency, with the greatest improvement exceeding 16%, all while maintaining precise oil supply to the high-speed bearings.

The research of unclear influence of air ingestion on the characteristics of squeeze film damper (SFD) oil film was carried out. The fluid domain was modeled. Influences of air ingestion were analyzed under different structure and working conditions. Mechanism of air ingestion on the characteristics of oil film was revealed. Results uncover that air ingestion occurs at the outlet boundary and have a significant inhibition on the cavitation effect. It is affected by whirl radius, clearance ratio, width, and oil supply pressure. Air ingestion has significant effects on maximum pressure, oil film force, moment at time T, oil film force in the x direction, oil film force in the y direction, oil film resultant force, and minimum pressure fraction. Moreover, the stability of damping and stiffness is improved due to air ingestion. Increasing aspect ratio, oil supply pressure, and reducing whirl frequency can improve dynamic characteristics. The results provide theoretical basis for the optimized design of SFD.