Abstract
On-board rotating machinery subject to multi-axial excitations is encountered in a wide variety of high-technology applications. Such excitations combined with mass unbalance forces play a considerable role in their integrity because they can cause parametric instability and rotor–stator interactions. Consequently, predicting the rotordynamics of such machines is crucial to avoid triggering undesirable phenomena or at least limiting their impacts. In this context, the present paper proposes an experimental validation of a numerical model of a rotor-shaft-hydrodynamic bearings system mounted on a moving base. The model is based on a finite element approach with Timoshenko beam elements having six degrees of freedom (DOF) per node to account for the bending, torsion and axial motions. Classical 2D rectangular finite elements are also employed to obtain the pressure field acting inside the hydrodynamic bearing. The finite element formulation is based on a variational inequality approach leading to the Reynolds boundary conditions. The experimental validation of the model is carried out with a rotor test rig, designed, built, instrumented and mounted on a 6-DOF hydraulic shaker. The rotor’s dynamic behavior in bending, torsion and axial motions is assessed with base motions consisting of mono- and multi-axial translations and rotations with harmonic, random and chirp sine profiles. The comparison of the predicted and measured results achieved in terms of shaft orbits, full spectrums, transient history responses and power spectral densities is very satisfactory, permitting the experimental validation of the model proposed.
Highlights
Rotating machinery subject to base motions, so-called on-board rotor, is a common feature in many industrial fields
Examples include a helicopter turbo-engine subject to airflight maneuvers and spectral lines associated with rotor blades, a turbopropeller suspended from an aircraft wing excited by the aerodynamic forces of a broad frequency range, and a spatial turbopump undergoing pyrotechnic shocks
The same power spectral density (PSD) is built for the only two mono-axial accelerometers involved in the driving process of the 6-degrees of freedom (DOF) shaker, with a theoretically nil cross-correlation between each other
Summary
Rotating machinery subject to base motions, so-called on-board rotor, is a common feature in many industrial fields. Among the few cases was the work done by Sousa et al [29] who built an on-board rotor test bench composed of a slender shaft with a constant circular cross section and a disk supported by ball bearings This rotor was excited by its base with a mono-axial electrodynamic shaker reproducing shock and sinusoidal base translations. The purpose of the present paper is to overcome all these issues by proposing a novel and complete experimental study in order to validate an on-board rotor model developed previously in [32] The latter has six DOFs per node to account for all bending, torsion and axial shaft motions. A 6-DOF hydraulic shaker is used to subject the rotor to base excitations
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