The effects of torsional-lateral coupling on the dynamics of a gear coupled rotor

Abstract

This thesis focuses on the torsional-lateral interactions seen in gear coupled rotors. Of particular interest are cases where the torsional stiffness parameters affect the lateral critical speeds and where lateral stiffness and damping parameters affect torsional critical speeds and amplitudes. A common procedure for critical speed calculations has been to solve lateral and torsional systems separately. This procedure is tested through an eigenvalue analysis. It is shown in this thesis, however, that torsional-lateral interactions play major roles in each other's critical speeds. Some research has seemingly uncoupled two lateral degrees of freedom from the gear system by choosing bearing forces and a coordinate system pointing along the line of action and normal to the line of action. This simplification method has been tested for cases when the lateral bearing stiffness becomes asymmetric. The force generated by a rotating imbalance also creates a variable moment arm as the center of mass rotates about the geometric center of the gear. This variable moment arm is commonly neglected, but is included in the last case study and its effects are displayed in the results section of this thesis.