A rig for testing lateral misalignment effects in a flexible rotor supported on three or more hydrodynamic journal bearings

The vibration behaviour of statically indeterminate rotor-bearing systems with hydrodynamic journal bearings is predicted to be significantly dependent on the relative lateral alignment of the bearing housings (i.e. system configurations). To validate this, a rig wherein the rotor is supported on four bearings is being designed. This paper describes the salient features of the rig which is shown to be capable of traversing several critical speeds over its operating range, to be capable of whirl instability, and to be capable of a wide range of lateral misalignment combinations which result in significant vibration amplitude changes. Appropriate instrumentation will enable bearing reaction forces and rotor motions to be measured for various speeds, unbalance and system configurations. Theoretical results suggest that the rig is well suited for misalignment identification experiments though the predicted ability of different system configurations to yield virtually identical vibration response emphasises the need for careful experimental design.