Bending-torsional coupled vibration of a rotor-bearing-system due to blade-casing rub in presence of non-uniform initial gap

In most of investigations on rub, the initial gap between blades and casing is considered to be in uniform distribution around the circumstance. Actually, due to several factors, such as flight loads, thermal loads and coating inhomogeneity, the initial gap may be non-uniform. The aim of this paper is to gain insight into bending-torsional coupled vibration of a dynamic model of an aero engine subjected to blade-casing rub in presence of non-uniform initial gap. At first, a rotor-bearing-system is modelled, in which a non-uniform gap exists in on location or multiple locations. Utilizing the impact experiment performed at a rotor test rig, the Lankarani-Nikravesh model is proved to be able to reveal the impact mechanism between blades and casing under a non-uniform initial gap. In the tangential direction, the Coulomb model is applied to describe the friction characteristics at the contact points. After that the bending-torsional coupled vibration of the system is solved numerically and the response in the presence of a non-uniform gap is determined. Additionally, the effects of the features of the non-uniform initial gap are examined. (C) 2019 Elsevier Ltd. All rights reserved.