A Simplified and Efficient Analysis of Morton Effect

The Morton Effect refers to a phenomenon of special instability for rotors supported by fluid-film-bearings and present with asymmetric heating for the journal part. This problem tends to occur when rotors exhibit synchronous vibrations. Originating from the temperature gradients during the eccentric orbiting of rotor journals, the Morton Effect has been a latent threaten to rotor stability since the fluid-bearing-supported rotating machinery was first in service. This paper extends the modeling scope to a general scenario when the heating source is not limited only to the viscous shearing effect. Such an extension could apply to the Newkirk effect, a problem induced by light rubbing but exhibiting similar phenomenon as the Morton Effect. The simplified coupled model enables the coupling between the thermal field and structural vibrations directly. To better understand the roles played by the thermal factors in the Morton Effect, this paper extracts the influence of temperature increase in the bearing fluid film on bearing dynamic coefficients. The investigation results show that the temperature rise, an accompany of increased speeds, has a significant influence on the cross-coupled stiffness coefficients but a negligible impact on other components of dynamic coefficients. In general, the speed plays a dominant role in the change of dynamic coefficients. In the end, the coupled dynamic model is validated by a case study of a mid-span rotor model investigated in the literature. Good agreements with the reference imply that the model assembled here is effective and reliable for the analysis of the Morton Effect.