Validation of a squeeze-film-damper test rig by using multibody cosimulation

Abstract

Squeeze-film dampers (SFD) are applied to provide damping at the outer ring of ball bearings used in jet engines. The main functions are to cap rotor oscillations and to reduce dynamic forces. A new test rig was designed to allow an orbital motion of the rotor shaft excited by two independently controllable electromagnetic shakers. In order to achieve this excitation, the two shakers are rigidly coupled together; due to this, a degree of freedom is missing in this mechanism. The precisely adjusted stiffness of the coupling elements acts as a solid joint to provide the missing DOF. The resulting shear forces acting on the opposite shaker are supported by a support structure, designed as part of the coupling elements. A multibody cosimulation and several other virtual studies are performed to verify and validate the dynamic behavior of the test rig. The SFD behavior cannot be implemented in the cosimulation by using a standard library damping element of the simulation tools because its behavior is nonlinear due to its design and functionality. It is implemented according to its valid theory, based on Reynolds equations for plain bearings. The calculation of the multibody physics takes place in MSC Adams, whereas the theory of the SFD is described and implemented as a mathematical model in MATLAB/Simu link. A both-ends-against-the-middle approach is realized and discussed.