Transient rotordynamic thermal bow (Morton effect) modeling in flexure-pivot tilting pad bearing systems

Abstract

The Morton effect (ME) is a thermally induced rotodynamic instability problem frequently reported in the fluid film bearing system. The temperature difference across the journal circumference may cause large spiral, synchronous vibration. Earlier ME modeling approaches rarely focus on the flexure-pivot bearing (FPB), significantly disproportionate to its wide application. Hereby, the transient ME prediction algorithm is proposed based on a high-fidelity thermo-elasto-hydrodynamic FPB model. A hybrid finite element analysis is adopted to evaluate the entire rotor thermal bow profile including the rotor midspan. The algorithm is benchmarked with experiments and applied to a realistic compressor model. Simulations confirm the proneness of the FPB system to the ME instability, and reveal the ME sensitivity to the bearing-rotor configuration and operation conditions.