Simulation Validation of a Coupled Blade-Shaft System Including Non-Linearity and Gravity Effects

A shaft-bladed-disk rotor configuration has been experimentally subjected to synchronous and asynchronous dynamic excitation using the test rig named Asynchronous Rotor Excitation System (ARES). This work covers validation of an advanced dynamic simulation of the complete system that is formed by this rotor supported on a static frame that provides non-axisymmetric support stiffness. Different sensors have been placed in this installation: displacement sensors at bearings and shaft, and strain gauges at blade roots to derive blade tip displacements. Comparison of test sensors with regard to simulation model results, under prescribed synchronous and asynchronous excitations has been performed, resulting in a very good matching of resonance frequencies and response magnitudes at bearings and shaft. Resultant modes have a significant degree of coupling between blades and shaft. Gravity load dynamic excitation has been also simulated to match blade tip displacement measurements. Gravity load is a non-axisymmetric static load that promotes dynamic excitation: a rotor blade experiences gravity load as an alternating load due to blade rotation. This type of loading is designated as 0EO (zero engine order) in the stationary frame as it remains at zero frequency at all rotor speeds. Blade root attachment to disks include non-linear contact effects that can be observed from blade tip displacements obtained from tests. Non-linear modelling of this blade root is also covered with a simplified model in order to explain observed behaviour during testing. In aircraft engines, due to flexibility of rotor blades and disks, critical modes can be coupled modes of disks and blades with shafts and, also, with static parts. Correct simulation of the complete system should include rotors and static parts in a single model. Rotors should include all steady-state rotatory effects: stress stiffening, spin softening and gyroscopic effect. This advance dynamic simulation technique of these systems has been validated in ARES. Also, specific non-axisymmetric static load conditions at aircraft engines i.e. cross wind scenarios (like gravity) can promote relevant vibrations. This 0EO excitation conducts to a specific dynamic solution that has been also validated in ARES rig through gravity load scenario.