Non-linear description of floating ring 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 Poincaré 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.