Dynamic modeling and nonlinear analysis of a rotor system supported by squeeze film damper with variable static eccentricity under aircraft turning maneuver

Abstract A high-speed rotating rotor system mounted on an aircraft is inevitably induced by parametric excitations, inertial forces and gyroscopic moments caused by maneuvering flights. With the increase of maneuverability, this effect becomes more significant, which may lead to severe vibrations and even abnormal operation. Using Lagrange's principle, equations of motion for a squeeze film damped rotor system relative to a maneuvering aircraft are derived, considering additional inertial forces and variable static eccentricity of journal, of which the mechanism and computation procedure under turning maneuver are analyzed and proposed. The effects of flight status, structural parameters, and operating conditions on transient responses are discussed, including forward velocity, turning radius, rotating speed, mass unbalance, and elastic support stiffness. The results indicate that when an aircraft negotiates a turn, the offset direction of whirl orbit is determined by centrifugal acceleration and gyroscopic moment. The journal whirls around variable static eccentricity, of which the magnitude is related to maneuvering loads and supporting stiffness. Increasing forward velocity or decreasing turning radius, the rotor vibration will enter earlier into or withdraw later from the relatively large eccentricity. During maneuvering flight, rotating near critical speeds and excessive mass unbalances should be prevented. The elastic support stiffness has a great impact on vibration behavior of rotor system in maneuvering flights. Using finite element modeling combined with mechanism analysis, dynamic characteristics of rotor system supported by squeeze film damper (SFD) under aircraft maneuver can be predicted, which provides theoretical and technical support for dynamic design of engine's rotor system mounted on aircraft with high maneuverability and agility.