Finite Element Modeling and Dynamic Analysis of Propulsion Rotor System

Abstract

Present work focuses on modeling and dynamic analysis of a marine propulsion shaft supported on three radial bearings and one thrust bearing. The motions of rotor and bearings are under the influence of each other and therefore such a system requires structural dynamic studies. Initially the rotor bearing system is modeled with 45 degree of freedom finite element model to obtain the natural frequencies. Internal unbalance force due to eccentricity of mass act on the propeller. Unbalance response of the rotor are obtained from Newmark time integration scheme. Effect of speed, bearing stiffness on the dynamic response is studied. In further case, the radial springs are replaced with three ball bearings, which are modeled by Hertz contact forces expressed in terms of the corresponding nodal displacements. The nonlinearity effect is further illustrated for the same rotor operating at different speeds in terms of time and frequency domain responses. Generalized GUI developed on MATLAB for stability analysis of shaft is very much useful for the users for parametric studies.