The whirl direction and characteristics of rotor system under maneuvering flight

Abstract

Maneuvering flight can generate the asymmetry of the stiffness or damping to an engine rotor system, as so to influent the whirl direction and characteristics of rotor system. In this article, the identification method for orbit direction is provided for a rotor system under maneuvering flight condition. By a simulation example, the variable movement shapes about rotor under maneuvering flight are illustrated through cases as the mixed and the pending whirls. The results show that the original low-order critical speed in the backward or forward whirl mode changes to the mixed whirl while considering the impact of maneuvering flight, where some backward and forward critical speeds in the same order are almost overlapped as one critical speed which in the mixed whirl mode. Maneuvering flight results in dynamic eccentricity of the rotor shaft, and the orbits of nodes in the mixed whirl are a series of ellipses with variable inclination angles. The case with pending whirl direction is finally determined as a mixed whirl by the orbit direction graph. The whirl directions of orbits on bearings or the contact angle of bearings maybe different under maneuvering flight can be explained from the rotor dynamical view.

Analysis of the effect of maneuvering overload on the reaction force of the main shaft bearing in aero-engine

“…The axial load depends on the aerodynamic load of engine compressor blades, while the radial reaction force is related to unbalanced excitation and additional excitation caused by maneuvering overload [1] Generally, the unbalanced excitation affects vibration characteristics of the rotor system [2][3], and furtherly, it affects the dynamic characteristics of the bearings reaction force. The maneuvering overload will results in dynamic eccentricity of the dual-rotor [4][5][6][7] and the impacts on the bearings reaction force are more significant. In some cases, an engine rotor system will have bending-torsion coupling vibration, which will change the frequency characteristics of the bearings reaction force.…”