Experimental identification of dynamic coefficients of lightly loaded tilting-pad bearings under several lubrication regimes

Abstract

This paper presents the identified dynamic coefficients of a lightly loaded actively lubricated bearing under three lubrication regimes: passive, hybrid and feedback-controlled. The goal is to experimentally demonstrate the feasibility of modifying the bearing dynamic properties via active lubrication. Dominated by the latest two regimes, the bearing properties become adjustable or controllable due to the injection of either a constant or variable pressurized oil flow. Such a flow is regulated by a hydraulic control system composed of (a) a high-pressure oil supply unit, (b) servovalves, (c) radial injection nozzles, (d) displacement sensors and (e) well-tuned digital controllers. A scaled-down industrial rotor featuring active lubrication, composed of a flexible rotor supported by a four-rocker load-between-pads tilting-pad bearing under light load condition, is used for this objective. The experimental identification is performed by means of measured frequency response functions and a rotor finite element model. Predicted coefficients are also provided for benchmarking. Comparing results between the different regimes, presented along with their expanded uncertainty, provides the experimental evidence of the bearing properties modification via active lubrication.