Grease lubrication of the high-speed ball bearing for small turbomachines

The feasibility of the operation of a mainshaft ball bearing with grease lubrication at high speed has been demonstrated by rig tests. Angular contact ball bearings of 8 mm bore were used under the 137 N axial load. In order to achieve a good reliability of the grease lubrication at very high speed, the bearings have been subjected to a variety of hostile tests, including the snap accelerations from 0 to 100000 rpm within 10 seconds, extended operation at high axial loading, operation at high speed, and operation exposed to hot air at turbine inlet. From extensive experiments, it was found that the bearings could be operated up to the speed of 0.87 million DN with grease lubrication, and a low-cost grease lubrication system was developed for an expendable small turbomachine.