Dynamic characteristics of rub-impact on rotor system with cylindrical shell

Cylindrical shells are widely used as rotating components in turbo-machines. Radial rub-impact contact tends to occur between the rotating shells and the stator due to the small gap and high speed of rotation. In this paper, a new model is developed to simulate the rub-impact contact force between the rotating shell and stator in the rotor system, where the effects of the geometrical parameters and deformation angular position of the shell on the contact stiffness are taken into account. The curvature variation of the shell subjected to rub-impact contact is defined using the transformation of the Fredholm Equation of the second kind, which is expressed as a function of the shell thickness and radius, the radial rubbing loads and the contact region term. Then, the formulation for the shell deformation is derived, and the relation among the contact region, deformation and forces is obtained. The rub-impact contact model is validated by comparing with the traditional piecewise-smooth linear-elastic contact model and the finite element analysis results. The proposed rub-impact contact model is introduced into the dynamic model of the rotor system with a cylindrical shell using the Sanders shell theory. Dynamic characteristics of the rotor system under two types of rub impact are investigated by analyzing the waveform, frequency spectrum, orbits, the rub-impact force distribution and motion stability. The effects of cylindrical shell on the dynamics of rotor system are evaluated. The proposed rub-impact contact model is capable of simulating the rub impact behaviors of complex rotor systems involving cylindrical shells more accurately. (C) 2017 Elsevier Ltd. All rights reserved.