Non-Linear Description of Floating Ring Bearings Rotordynamics

Floating ring bearings are commonly used in automotive turbochargers for their low manufacturing costs. However, the strong non-linearity of this configuration prevents the use of traditional rotordynamic techniques to describe their behaivior, thus relegating its design process to a costly trial and error process. A numerical characterization of this non-linearity is hereby presented for a flexible rotor supported on two FRBs. Non-linear techniques such as Poincare´ and Bifurcation maps, along with traditional rotordynamic techniques, show ranges of periodic, quasiperiodic, and chaotic motion, being the most stable ones related to high unbalance and/or low speeds, though in some cases the periodicity of the motion is reestablished at higher speeds. In all cases chaos is reached through a period doubling route. Shaft flexibility is shown to retard the occurrence of chaos, while excitation of conical motion seems to favor it.