Experimental analysis of the hydrodynamic effect during start-up of fixed geometry thrust bearings
Résumé
Most of the investigations on thrust bearings were performed under a steady-state condition and this regime is now well understood. Contrary to this, the behavior during the first period of start-up is sparsely studied. Start-ups of thrust bearings are critical periods where a mixed lubrication regime occurs. This regime can be detrimental for the lifetime of the system. It is usually mentioned in the literature that the textures act as micro reservoirs which can be beneficial to help lift-up during start-up. This is an intuitive hypothesis and there are no experimental results to prove it. This study uses an experimental approach in order to analyze the behavior of different kinds of thrust bearings with fixed geometry. It mainly focuses on the capability of textured thrust bearings to lift up during start-up. This study shows that only specific texture geometry can help the formation of a fluid film. The results are compared to those obtained with classical geometries like tapered land, pocketed and untextured flat-land thrust bearings. The original results show a relatively good ability of flat-land thrust bearings to generate a lift-up during the start-up period.
An experimental device is used to measure, at high frequency, the friction torque as well as the electrical resistance across the fluid film to determine the lubrication regime. The comparative analysis allows us to explain the factors which modify the contact.