The tilting-pad journal bearing in the cooling system of the nuclear power plant is equipped below the ground and vertically positioned to accomplish its function for water transfer. Usually, the loading conditions are relatively stable since the required water volume almost remains the same level during the operation, but the loading direction cannot be known in advance. Furthermore, the bearing is designed with several separate pads, which allows the bearing to support the loading flexibly. The safety application of nuclear energy requires the bearing to have a reliable ability to maintain the rotating motion of gear sets. This study develops a numerical model to simulate the mixed thermo-elastohydrodynamic lubrication for the tilting-pad journal bearing in the nuclear plant. The elastic and thermal fields are properly determined, and the induced displacement is taken into account for an accurate description of film thickness. The asperity contact due to misaligned journal is well evaluated in the local area where the lubrication film cannot separate the surfaces. A parametric study is undertaken in detail to reveal the aspects that influence bearing lubrication. The conclusions potentially provide fundamentals for further lubrication optimization of the bearing system.

This study presents a generalized model of mixed elastohydrodynamic lubrication, in which the dimensional Reynolds equation is discretized according to a modified differential scheme based on the full analysis of the pressure balance within the lubrication region. The model is capable of a wide range of lubrication regimes from fully hydrodynamic down to boundary lubrication, and both the steady-state and the time-dependent conditions can be considered. A simplified computational procedure is proposed for elliptical contacts without the ellipticity parameters specified. The evolution of lubrication behavior at startup and shutdown conditions is investigated and the transient effect of surface waviness is discussed. The model application is then extended to contacts of multilayered materials, and the effects of the layer stiffness and the fabrication methods on the stress fields and lubrication performance are analyzed. The conclusions may potentially provide some insightful information for the design and analysis of functional materials and their engineering structures.

In this study, a numerical model is developed for the analysis of elastohydrodynamic lubrication (EHL) at transient conditions during startup and shutdown processes. The time-dependent solutions are derived from an iterative algorithm with surface roughness involved, and the initial value is specified as the solution of the dry contact for the startup or steady-state solution of the lubrication contact at the starting velocity for the shutdown. The technique of discrete convolution and fast Fourier transform (DC-FFT) is employed to improve the computational efficiency. Solutions for smooth surfaces are compared with those obtained numerically and experimentally, and good consistency can be found. Profiles of pressure and film thickness and contours of subsurface stresses are analyzed to reveal the effects of acceleration/deceleration on the lubrication evolution. An isotropic roughness is then taken into account for the analysis. It is concluded that the coupling effects of the lubricant cavitation and oriented roughness would result in complex profiles of pressure and film thickness due to their disturbances to the lubrication film. A machined rough surface is presented to demonstrate the generality of the model. The analysis may potentially provide guidance to estimate the behavior of mechanical elements.

The paper primarily employs the 3D calculation method of the helical gear-meshing line and meshing position, in addition to the traditional method of the gear-meshing stiffness calculation. This analysis and correction of load-sharing are beneficial for improving the assembly process of high-powered critical equipment. The dynamic models of rigid–flexible coupling, velocity–torque, and the meshing force of planetary gear trains in nuclear power plants are established based on the principles of gear dynamic characteristics. Based on an analysis of the vibration characteristics of a planetary gear train, a load-sharing method for the planetary gear train is proposed. This uniform load-sharing method is explored under different modification values to provide a reference for load-sharing research on high-powered key equipment. In this paper, a dynamic simulation analysis of the gearbox system is conducted, using virtual prototype software to study the load-sharing performance of the planetary gear system. Furthermore, via a vibration frequency analysis of the gear mesh force, the causes of planetary gear train vibration are discussed, particularly their impact on planetary load. This provides a basis for the assembly process of a nuclear power circulation pump gearbox, ensuring that the gearbox for the circulation pump has a longer life that meets the 40-year service life requirement, and provides a foundation for the study of planetary load characteristics.