A Modal Transient Rotordynamic Model for Dual-Rotor Jet Engine Systems

Abstract

A transient modal simulation model is developed for a “typical” two-spool jet engine configuration, consisting of a low-speed rotor, a high-speed rotor, and the supporting case structure. The formulation cited permits bearing connections from a rotor to the support structure and between rotors. A conventional Jeffcott-Green flexible rotor formulation is used to model each rotor as a collection of rigid bodies connected by a mass-less elastic structure. The case structure is similarly modeled as a collection of axisymmetric elastically connected rigid bodies. The transient modal simulation model development is based on eigendata for the complete structural dynamics model (elastically coupled rotors and case structure) at zero running speed. The completed model readily accounts for gyroscopic effects, bearing damping and nonlinearities, structural modal damping, concentrated damping due to oil-film dampers, etc. The applicability and utility of the model is demonstrated by the simulation of a turbine-wheel blade loss.