Numerical Simulation of the Flow in a Large-Scale Thrust Bearing

Abstract

Thrust bearing is a key component of large-scale water turbine. It closely relates to the efficiency of large-scale water turbines, and even determines whether the large-scale turbine can operate normally. With the development of the capacitance of water turbines, thrust bearing will develop to the direction of high speed and heavy load. The structure, strength, lubrication and the characteristic of heat radiation of large-scale thrust bearing were often researched in the past. To study the flow condition of the large-scale thrust bearing and analyze the load characteristics, CFD simulation was carried out on the model of thrust bearing. In this study, CFD method was used to simulate the internal flow field of the large-scale thrust bearing. The model researched was a thrust bearing for 1000MW water turbines. The diameter of the thrust bearing was over 5.8 meters, and the maximum thrust load of the bearing can reach to 60MN. The thin gap between the runner and the pad was usually neglected in the published CFD calculations of thrust bearing. But the thin gap was taken into account in this investigation. 1/12 of the model was used as the computational field and periodic boundary was used in the calculation. The standard κ-ε turbulence model was used to simulate the thrust bearing model, and the flow field in the thrust bearing was obtained. The thin gap between the runner and the pad is a wedge. The pressure and velocity distribution in the thrust bearing and thin gap was calculated respectively with conditions of different thin gaps and different rotational speeds of runner. After that, the relationship between carrying capacity and the size of clearance or the speed of the runner through analyzing the data has been obtained from the results of the calculation.

Transient thermo-elasto-hydrodynamic analysis of a bidirectional thrust bearing in start-up and shutdown processes

“…Due to the importance of the thrust bearing, huge efforts have been made by researchers to obtain its lubricating characteristics. The hydrodynamic (HD) analysis (Wang et al , 2010) only calculates the flow characteristics in the oil film, and the thermo-hydrodynamic (THD) analysis considers the viscous frictional heat inside the oil film based on the HD analysis (Fouflias et al , 2017; Zouzoulas and Papadopoulos, 2017; Lin et al , 2018). The calculation domain of the HD and THD analysis is only the oil film; thus, there are several shortages: (1) In order to obtain the dynamic and static characteristics of journal bearings more easily, Reynolds equation neglects the influence of inertia term, oil film curvature, radial flow field, the pressure difference in the direction of the film thickness and the turbulence in the flow; (2) The finite difference method commonly used to solve the Reynolds equation ignores some geometric details such as the oil groove on the pad surface and the chamfer of the oil inlet; (3) The boundary pressure, temperature of the oil film as well as the heat transfer coefficient between the pad surface and the lubricating oil are assumed respectively.…”