Host: The Japan Society of Mechanical Engineers
Name : The 15th International Conference on Motion and Vibration(MoViC 2020)
Date : September 09, 2020 - September 11, 2020
Some examples of subsynchronous vibration occurred in the starved condition bearing are reported, for example, in the API 684 Standard Paragraph it is introduced that the subsynchronous vibration experienced in the high-speed balancing test facility in the vacuum condition and the cause is confirmed to be the starvation of bearing. Because in the vacuum condition of the test facility the pressure inside the bearing housing was low and estimated to be starved. In this example after installing the proper end seals in the bearing housing can increase the pressure inside of the bearing housing and avoid the subsynchronous vibration.
As the authors experienced the similar operation in the actual machine in the same situation in the high-speed balancing facility. The rotor type is a back- pressure steam turbine for the turbo generator unit. The bearing types is 5 pad tilting pad bearing. The effects of starved oil film on the subsynchronous vibration was doubted. But generally, the fluid film analysis in the starved bearing cannot be performed because the fluid film will not be established correctly. Therefore, the analysis in this paper is tried applying smaller size bearing pads to simulate the estimated remaining oil film sizes with carrying same bearing load. The size of bearing pads is changed parametrically depending on the estimated starved oil film.
In the current stage it will be difficult to know the starved oil film size or remaining oil film size correctly. But the effects of the estimated starved film condition on the stability in rotor can be evaluated by applying dynamic analysis to the rotor-bearing system. From the results the excessive small damping ratios in the system could be obtained and the estimated starved bearing film condition was simulated.
