JOURNAL BEARING DIFFERENTIAL HEATING EVALUATION WITH INFLUENCE ON ROTOR DYNAMIC BEHAVIOR

The nature of differential heating across the journal of a hydrodynami cally lubricated bearing has been investigated theoretically and an as sessment made of the local thermal bend in the rotor at the bearing lo cation. The energy balance for the system is time dependent and involv es a stationary bearing component, an oscillating lubricant film, and a rotating, orbiting section of journal. Thermohydrodynamic solutions are developed which allow for temporal and spatial periodic variations of bearing, lubricant and journal temperatures. The influence of a sy nchronous journal orbit on the temperature distribution throughout the system is discussed. In particular, the relation between any prescrib ed orbit and the steady state temperature differential across the jour nal, resulting in steady state rotor bending, is established. The role played by such thermal bending in the onset of unstable synchronous w hirl in the rotors of high-speed machines is outlined.