Considerable amount of mathematical modeling backed by extensive experimental investigations have gone in to the study of the rotordynamics behavior of high speed turbo expanders. These investigations revolve predominantly around the linear & non-linear aspects of hydrodynamic bearings that support these rotating elements. Further, these expanders are not mechanically coupled to the prime mover and hence the impact of lateral vibrations imposed by the interfacing assemblies downstream is not a concern.
However, when the expander is mechanically coupled to a prime mover, say by means of gears, lateral vibrations resulting from the interfacing system is going to have a pronounced effect on the rotordynamics behavior of this system. It is of paramount importance that we account for the stiffness & damping properties of the interface components in order to accurately predict the rotordynamics behavior of the expander.
An attempt is being made by the authors to develop an expander and bearing system along with a high speed, multi stage reduction gear box, to understand the impact of lateral vibrations due to mechanical coupling of the expander.