Abstract

Tilting pad journal bearings are widely used in High-speed rotating machinery such as turbine generators to support rotating shaft stably. However, reduction of the bearing loss is required for increasing generator efficiency because the bearing loss accounts for approx. 10 % of the total loss in the generator. Generally, the bearing loss is caused by shear resistance of oil around rotating shaft and increases in proportion to amount of lubrication oil. In recent years, the reduction of the supply oil flow rate has been promoted in order to reduce the bearing loss. However, if the oil supplied to the gap (oil film) between the rotating shaft and the pad are insufficient, oil film pressure is decreased due to insufficient lubrication, which may increase the Sub-synchronous vibration of the rotating shaft and the pad. In this study, the developed method for predicting increased the Sub-synchronous vibration caused by insufficient lubrication and the developed method for reducing the Sub-synchronous vibration with a minimum amount of oil supply are shown. Furthermore, the effects of reducing the Sub-synchronous vibration and the bearing loss are shown by testing using the developed method for actual products.