Influence of jacking oil pocket configuration on the static and dynamic performance of tilting pad journal bearings

Tilting pad bearings have become a good choice for steam turbine generator because of its safe and stable performance. But during the start-up process with low speed, it often fails to form the safe enough oil film. It will result in the direct contact between the journal and the bearing, then causes significant friction on the journal and bearing surfaces. In order to reduce this phenomenon, the jacking oil pocket is usually machined on the bearing pad. With the jacking oil pocket, the load capacity of the bearings will also change. This study investigates the effect of jacking oil pockets on the performance of tilting pad journal bearings during low-speed start-up and steady-state operation. A TEHD model is developed to analyze the influence of pocket geometry and distribution on load capacity, pressure, and temperature. Through numerical calculation, the influence of different numbers of oil pockets and different arrangements of oil pockets on the bearing's bearing capacity is further calculated. The study shows that the opening of the jacking oil pocket has a large impact on the static performance of the bearing, and has little impact on the dynamic performance of the bearing. But they will adversely affect steady-state performance if not optimally designed.