Dynamic analysis of slender rotor of vertically suspended centrifugal pumps due to various hydraulic design factors

If a rotor is excited at one of its natural frequencies, a resonance occurs. The resonance can lead to large amplitude oscillations and subsequently failures. Field experience proves that the excessive vibration of the rotor of centrifugal pumps shows itself in wear and fatigue failure of shafts, bearings, wear rings, seals and impellers. So, modal analysis of a pump rotor is of great concern to researchers, international standard organizations and industries. In this research, dynamic behavior of a nonlinear finite element model of slender rotor of vertically suspended centrifugal pumps is studied. The dynamic model of the rotor is discretized into an appropriate number of three-dimensional Timoshenko beam elements. In addition to the main nonlinear terms and particularly the geometric stiffening effect, the gyroscopic effect has been also taken into account. The full-order equations of the motion, which are obtained by the Lagrangian approach and the finite element method, are integrated into a computational plan. The ability of the recent nonlinear dynamic model, which is intended to furnish a basic model for further development of a more comprehensive model, is examined to track the coupling between different types of vibrations. The comprehensive modal analysis of the rotor due to various hydraulic design factors is presented.