Abstract:

The dual challenges of critical speed prediction inaccuracies and ambiguous vibration behaviors are present in high-speed flexible rotors, particularly in free turbine rotors in turboshaft engine systems. The study begins with an examination of the rotor-bearing bidirectional coupling mechanism, with a primary focus on the nonlinear characteristics of the bearing. An investigation is carried out on the mechanical modeling methodologies for four-point contact ball bearings (FPCBBs) and cylindrical roller bearings (CRBs). To address the issue of excessive computational time in traditional bearing calculation methods, the sled dog optimization (SDO) algorithm is substituted for the conventional Newton-Raphson method. A rotor-bearing coupling dynamics model is developed by the finite element and lumped mass methods, with experimental validation achieved through a simulator test rig. The effects of three internal bearing parameters in FPCBBs (arching width and raceway groove curvature coefficient) and CRBs (initial radial clearance) on the critical speed characteristics and vibrational behavior of rotor-bearing coupled systems are examined. The numerical simulation results show some interesting conclusions.

Key words: critical speed, vibration behavior, sled dog optimization (SDO) algorithm, rotor-bearing coupled system