Active adaptation of a gas foil bearing system for high-speed rotor dynamics control

Abstract

A control strategy in a gas foil bearing with adaptive configuration is proposed in this work to enable operation of rotating shafts in extended high-speeds. The electromechanical system claims to control high-speed rotor dynamics by applying model predictive configurations of the top foil structure, utilizing a set of piezoelectric actuators located in the bearing’s circumference. Optimal configurations of the top foil are predefined through a GA optimization procedure to retain damping ratio of the rotor-bearing system above a threshold. The optimal configurations account for operability and integrity constraints like minimum gas film thickness and gas temperature rise. The dynamics of the rotor, the coupled thermo-elasto-aerodynamic lubrication problem, the foil structure dynamics, and the actuator dynamics define a multi-physical model in an autonomous (balanced rotor) or non-autonomous (unbalanced rotor) state space. Shaft’s thermal expansion and radial deformation due to centrifugal forces are taken into account in the analysis, while the piezoelectric actuator models account for hysteresis. The virtual experiments consider journal diameters of up to 100 mm and demonstrate that the operability of the system is extended to circumferential journal speeds approaching the sonic speed. Operating parameters related to the operability of the piezoelectric actuators and the integrity aspects of deformation and temperature in the components of the electromechanical assembly are presented for the selected case studies, and found to be acceptable.