Some experiments on oil whirl and oil whip

The oil whirl and oil whip phenomena have been well known since the early twentieth century. However there is a lot of confusion on the parameters that affect the onset of instability. In this study, we investigate the onset of instability, on a flexible rotor mounted on two plain cylindrical journal bearings. The rotor is run through the first critical speed, the instability, and the second critical speed. Tests are conducted at various unbalance levels, pressures, and misalignment conditions on the coupling. It is shown that, by far the misalignment of the coupling is the parameter that is most effective on the onset of instability In particular angular misalignment resulted in the smoothest rotor response.